In This Article
No Perc, No House
Deep Hole Test
Perc Testing
Setbacks & Clearances
Options if Site Fails
Post Comments & Questions
View Septic System FAQs
View all SEPTIC SYSTEM articles
Traditional septic systems only work if the soil in the leach field area is sufficiently permeable that it can readily absorb the liquid effluent flowing into it. Otherwise, untreated effluent may back up and pool on the ground surface.
Also, there must be at least a few feet of good soil from the bottom of the perforated leach pipes to the rock or impervious hardpan below, or to the water table. Much of the treatment takes place in this soil layer.
Less commonly, a site can fail because the soil is too permeable, allowing the effluent to reach the groundwater before it is fully treated. Very steep slopes are also unsuitable for a conventional leach field.
The specific standards vary from town to town, but any of these characteristics can prohibit the use of a standard gravity-fed septic system. In some cases, a more expensive alternative septic system may be allowed. To determine is a building site is suitable for a septic system, a percolation test (typically called a “perc test’ or “perk test”) is required.
NO PERC, NO HOUSE
On rural sites without municipal sewage systems, a failed perc test means that no house can be built – which is why you should make any offer to purchase land contingent on the site passing the soil and perc tests. As prime building sites become increasingly scarce (or prohibitively expensive) in many parts of the country, rural sites that will not pass a percolation or perc test are increasingly common.
In general, soils with high sand and gravel content drain the best and soils with a high clay content or solid rock are the worst. Most soils fall somewhere in the middle with a mix of course sand and gravel particles, small silt particles, and miniscule clay particles – the smallest.
To get a rough idea before investing time and money in testing, dig below the top few inches of topsoil (loam) to the lighter soil beneath and grab a handful. If the soil has a sticky, damp texture, and you can form a small lump of damp subsoil into a long, thin ribbon or worm shape that holds together, then the soil has significant clay content.
If you can form a ribbon of soil 2 in. or longer in the ribbon test, it indicates that the soil has high clay content and may fail a standard perc test.
The two main tests used to determine a site’s suitability for a septic system are a perc test and visual observation of the soil in a test pit, sometimes referred to as a deep hole test. Testing requirements vary greatly from state to state and often from town to town, as most states allow individual towns to establish separate rules within state guidelines.
So make sure you talk to your town health officer about what tests are needed, when they can be done, and who should perform them. Whether or not a licensed professional is required, it’s a good idea to hire a seasoned expert with local experience as many of these tests have a bit of wiggle room.
DEEP HOLE TEST
Most evaluations start with a deep hole test dug by machine to well below the bottom of the proposed leach field – often 7 to 10 feet deep or greater. Testers are looking for the high water table, and the presence of rock ledge or impermeable soil that will block absorption of water. In some areas, testers also evaluate the soil for drainage characteristics. Soil samples may be taken back to the lab, or visual observations of the soil layers may be sufficient. In many jurisdictions, the absorption rate of the soil is measured in the field with a perc test.
Visual observations are used to identify the “limiting zone,” where the soil is unsuitable for treating sewage. This is determined by upper layer of the water table, or impermeable soil or rock.
The seasonal high water table is identified visually by looking for “mottling,” splotches or streaks of color in the soil indicating the occasional presence of water. Examiners also look for layers of rock or impermeable soil and may send soil samples to a lab.
If the limiting zone is too close to the surface to allow for a conventional leach field, then a mound or other alternative septic system may be required. Typically, the water table or impermeable soil must be at least 3 feet below the bottom of the trenches in the leach field, but the exact distance varies with local regulations.
While most soil experts believe that soil observation can provide enough information to design an effective septic system, most states today also require perc testing to directly measure the rate at which water percolates through the soil. The test measures how fast water drains into a standard-sized hole in the ground. The results determine whether the town will allow a septic system to be installed, and system designers use the results to size the leach field.
SEASONAL HIGH WATER TABLE
Some municipalities may also require direct testing of the seasonal high water table under certain conditions. For example, this may be required for some types of alternative systems or in areas with a known high water table. The usual approach is to drill small monitoring wells, also called piezometers.
The monitoring wells are essentially plastic pipes stuck into holes drilled in the ground. During the wettest part of the year, the depth of water in the pipes is measured. For a system to be approved, there must be adequate clearance from the bottom of the drain field trenches to groundwater.
PERC TESTING
To conduct a perc test, first talk to the local health department official as requirements can vary significantly from town to town as far as who can conduct the test, the minimum number of holes, depth of holes, required absorption rates, and when the tests can be performed. In general, tests cannot be conducted in frozen or disturbed soil, and some areas only allow tests during certain months of the year when soils tend to be wetter – so plan ahead.
Test procedure. A typical perc test consists of two or more holes dug about 30 to 40 feet apart in the proposed drain field area (see illustration). The holes are typically 6 to 12 inches in diameter and 2 to 3 feet deep, the typical depth of the absorption trenches in a leach field. Next, you or the technician should place 2 inches of clean gravel in the bottom of the hole.
Scrape the sides of the hole with a sharp tool (nails driven through the end of a 1×2 work well) to loosen soil compacted during digging, and remove any loose soil from the bottom of the hole. Since the perc test is meant to simulate the actual conditions in a working septic system, the soil is then “pre-soaked” for several hours to saturate the soil. Keep adding water to maintain about 12 inches of water in the hole for at least 4 hours. Clay soils should soak for at least 12 hours to fully saturate.
The next day, clean out any loose soil that has fallen to the bottom, and carefully fill each hole with water to a depth of 6 inches above the gravel. Then measure how much the water drops in 30 minutes (or less for highly permeable soil that drains quickly). The times are then carefully documented and used to calculate the percolation rate – the time it takes for the water to fall one inch.
The percolation rate is usually expressed in minutes per inch of drop. A rate of 60 minutes per inch (MPI), meaning the water dropped one inch in 60 minutes, is often the cutoff point for a standard gravity-flow septic system, although the maximum number varies from 30 to 120 MPI depending on local regulations. Some towns require additional “hydraulic” soil tests for sites that test above 30 minutes per inch.
The cutoff for too-fast percolation is typically 1 to 3 minutes per inch. Below that, water absorbs too fast to be effectively treated before reaching the groundwater. The worst-performing hole is the one that counts. Some towns require that a town official be present to witness the test.
Perc test regulations vary a great deal from one town to the next. General ranges for soil permeability are as follows:
- Below 5 MPI: Highly permeable soil. Alternative systems may be allowed, including pre-treatment of effluent, pressurized dosing, or addition of denser soil around trenches.
- 5 – 60 MPI: Conventional leach field permitted.
- 60 – 120 MPI: Low-permeable soil. Alternative systems may be allowed, including pre-treatment of effluent, pressurized dosing, enhanced treatment, mound systems, and other alternative systems.
- Above 120 MPI: Very low-permeable soil. Alternative systems with enhanced wastewater treatment may be allowed under some conditions.
Test results are usually good for two to five years, and in some cases can be renewed. However, with all things perc, rules vary greatly from town to town so don’t make any assumptions. Always check with the town health department before proceeding.
OTHER SITE CONDITIONS
Septic system regulations vary widely, but most municipalities require that the leach field meet specific requirements above and beyond the perc test. Some common limiting factors are:
- Steep slope. The maximum allowable slope for a conventional system typically ranges from 20% to 30%.
- Filled land. Native soils are typically required, although engineered fill may be acceptable in some cases.
- Wetlands or flood zones. Not acceptable for leach field.
- Site drainage. The leach field should not be in the path of runoff during rain storms, which could cause erosion or flooding of the system.
SETBACKS & CLEARANCES
Minimum distances are required from the septic tank and leach field to buildings, property lines, water pipes, wells, and open water. On small sites, a variance might be required to allow sufficient space. You may be required to find suitable space for both the active leach field and a replacement field, for use in 20 or 30 years when the original field is exhausted. Clearances vary from one town to another. Typical minimum distances are:
| SEPTIC SYSTEM MIN. CLEARANCES (typ.) | ||
| Distance to | Septic Tank | Leach Field |
| House | 10 ft. | 10-20 ft. |
| Property line | 10 ft. | 10 ft. |
| Private well | 50 ft. | 50-100 ft. |
| Potable water piping | 10-25 ft. | 25 ft. |
| Open water (stream, pond, wetland, etc.) | 50-100 ft. | 100 ft. |
| Dry gulch/stream bed | 10 ft. | 25 ft. |
| Subsoil drains | 10 ft. | 25 ft. |
| Note: Always check with local codes | ||
OPTIONS IF SITE FAILS
Even if your site fails a perc or deep-hole test, all is not lost. On larger sites with more than one potential site for a drain field, you can test a second area. For sites with high water tables, you may be able to “de-water” the drain-field area by strategically placing gravel-filled trenches and subsurface drain pipes to conduct water away from the drain field. You’ll need a highly experienced earthwork contractor, and possibly the help of a civil engineer or geotechnical engineer, to make this work.
Also, a wide range of alternative septic systems have been developed in recent years for use on almost any type of site. Find out which systems are approved for use in your area and which might be suitable for your site. In general, these systems cost more and many require pumps, alarms, and other components that require more monitoring and maintenance than a standard septic system. Some require annual maintenance contracts to ensure that they continue to work properly.
As alternative systems become more common and more widely accepted, formerly unbuildable lots may become approved building lots. As with any new building technology, however, look for products and systems with a proven track record in the field. Also find a contractor who has first-hand experience installing the particular system you are considering. You don’t want to be the first one on the block to try out an unproven design. A failed septic system is not a pretty sight — or smell!
See Also:
Are Alternative Systems Allowed?
Chamber System Failure
How Much Slope For Septic Line?
Inspecting a Septic System
Lifespan of Septic System’
Minimum Lot Size For Septic System
Perc Test Cost
Perc Test: Best Time of Year?
Replacing Failed Drain Field in Same Location
Retesting a Site That Failed to Perc
Sand Filter for Existing System
Testing an Existing Septic System
Testing for a New Septic System
Wet Sites, Septic Systems For
Who Performs Perc Test?
View all SEPTIC SYSTEM articles
Jackie O'Brien says
Options After Failed Perc Test?
WOW, this website is the best thing on the Web! I just spent the morning reading all of the questions and your responses and I learned so much about perc tests, systems, etc. I now feel ready to “communicate” with our septic designer and the County Health inspector about the steps involved in a perc test.
We know our lot is very marginal for perking. Our septic designer/installer has confused us by talking over our heads and fast-talking, (He says to forget about building a house and just put a garage on the lot.) Our County health employees are not helpful and seem to not want our property to perc. (Which is weird because if we are able to build, the County will be able to collect massive property taxes. (Washington State—UGH!)
I do have a question I hope you can help with: …we were told by a neighbor that if the perc test fails we would be able to bring in fill and then build an alternate system because we would have a ‘failed perc test’ on file. We actually would like to build up the elevation of the property but haven’t done so because the perc must be done on “undisturbed” soil. We are open to an alternate system.
Does this make sense?
Thanks in advance.
Jackie
buildingadvisor says
The rules that govern septic system permitting are established by the town or county, often in combination with state law. In many states, local laws may be more restrictive than state law, but not less.
The authority who interprets and enforces the rules is typically the health or environmental department of your town or county. To complicate matters, the rules change over time, often getting more restrictive. In some areas, municipalities are trying to upgrade the performance of systems to deal more effectively with nitrates and phosphates, which can impact local lakes and bays. Traditional septic systems do a good job of eliminating disease-causing bacteria from wastewater, but do little to remove nitrogen and phosphorus. Over time, these can lead to algae blooms, oxygen depletion, and other serious problems in surface water.
As you point out, a marginal site that fails the perc test may be eligible for an alternative septic system (and some types of alternative systems address the issue of nitrate and phosphate reduction). However what specific types of alternative systems are allowed is entirely determined by the local authorities. The variety of alternative systems on the market and in development is mind-boggling, so help from an experienced system designer is essential to help you identify (and then design) a viable system. It’s always best to work with a local designer who knows the rules and the people who issue permits. There is usually some wiggle room in the morass of septic system regulations.
It is true that a conventional system generally needs to be installed on native soils. Engineered alternative systems, on the other hand, often bring in non-native soils to help process the effluent – for example, a mound system is built with sand and gravel fill placed on top of native soils.
Your desire to raise the elevation of the house should not be a problem as long as the leach field is installed over native soils.
If some type of alternative system is allowed on your site, you can expect to double or triple the cost of the septic system and expect annual maintenance costs to be higher as well. Some types of systems need ongoing monitoring and maintenance, often provided through a service contract. With newer systems that have not yet established a track record in the field, you also face the possibility that the system will malfunction or fail prematurely.
So yes, it’s possible that you can build on this site, but there is no guarantee. And if you do require an alternative system, choose one with a proven track record – not one on the bleeding edge if at all possible.
Emanuela Wiktor says
Can I Alter Septic System From Approved Plan?
We are under contract on a property in NC, it is two parcels sold together. One parcel is about 10.63 acres and the other is 8.8 acres, they are side by side. On the property that is 10.63 acres we want to build a our 4 bedroom house as well as a bardoniumium with about 900-1000 sq ft of living quarters for our parents. The other property of the 8.8 acres will be to build a wedding venue. For our perc test they want us to draw a site plan. Do we need to include all of the three buildings? Are we going to be stuck with were the house and septic tank goes once it is on the plan and they come out and test it in that spot?
Our broker told us not to include the bardoniumium and just put our house on the plan, but wouldn’t the perc test determine if its only suitable for that 4 bedroom house and not the additional 900-1000 sq ft?
Note: we wanted the house and bardoniumium to share a septic and well.
buildingadvisor says
Every municipality in the US has its own regulations for septic systems. And these rules are subject to interpretation by the local officials, usually in the health department, who oversee testing and permitting. So I cannot possibly know how they are going to react to your plans.
They may allow the two main structures to share a well and septic or they may not. Residential and commercial properties have different rules and two separate parcels are involved, so it’s gets complicated from a regulatory perspective.
I can tell you, however, that you are taking a big risk that you will be denied a permit for your “barndominium” if you leave it off the original site plan. In general, septic system permits are based on the number of bedrooms. If the barn structure contains any bedrooms, and the total number of bedrooms exceeds the capacity of your approved system, then it’s highly unlikely that it will be allowed.
If the additional structure were simply an outbuilding like a barn; then it might be approved — hard to say. You will need to run the entire project by the zoning department, as well, to make sure you are in compliance with zoning rules for both your residential and commercial structures.
And, yes, you will need to put the tank and drain field where they are shown on the plan. There is a little bit of wriggle room, but you can’t just build it where you want without additional testing and a new septic plan. The soil tests must be done in the location of the drain field.
Relying on a real estate agent for advice in these matters is also very risky. Their job is to sell real estate. The only advice I would listen to would be directly from the folks who hand out septic system permits.
Donna says
Bought Home With Undersized, Illegal Septic System
We would never have finalized purchase under said conditions. We are dealing with a huge septic issue because the land we live on use to have a mobile home on it in 1966. A home was built around the frame of the trailer in 1973. No permit exists and it was basically illegal to do what they did. So, we’ve been living in a 4 BR home with a septic system built for a 2 BR for over 11 years. The seller knew there were septic issues, but told us they would “take care of it”.
We have very limited land with space to install a max. 2 BR system. To complicate matters, we have non-perking soil. We’ve been quoted $55,000 for a BAT system.
josh says
This is a reply to an year-old comment, but I’m adding a response thinking perhaps it will help another person
1 – Once a manufactured home (trailer) always a manufactured home. No about of adaptation will change the classification. This is simply good to know.
2 – Again, this does not fix your problem, but I advise a buyer to always have a septic test. The septic was likely not illegal; simply times and rules have changed and the system would have been grandfathered in. My old farm house had a septic that was barely more than a bunch of cement blocks. It was fine until an untimely drive over by a heavy machine. The municipality would not allow a repair; the entire septic had to be brought to code.
Scott Williams says
How To Interpret Perc Test Results?
I had a soils analysis on a lot by the county Environmental Health dept. The official email stated 2 bedroom perc. However, on the phone the tester said the favorable soil was quite deep and for that reason would support an alternative system that would support 3 bedrooms. At the time I did not write down the name of this alternative. Does this sound familiar — is there a standard go-to system-type for limited area, but good depth soils? The man added that using modern flow-regulated plumbing might extend the site even more to 4 bedrooms.
Does the feedback from the site tester make sense?
buildingadvisor says
You really need to get back to the tester to see what type of alternative system he was suggesting. There is no “standard” alternative system. There are many alternatives and some are more widely accepted than others. The most common is a mound system, but this would not make sense for a site with deep, good soil. Mounds are mainly used on sites with marginal soils or inadequate depth of good soil (water table or hardpan/rock too near the surface).
Test procedures, interpretation of results, and permitting are different in every municipality. Even where there is governing state law, local regulations can be more stringent. In some areas, like yours, health department officials must perform or witness the perc test.
The health department should be able to tell you whether your site is suitable for a 2, 3, or 4 bedroom system based on the perc test results, and what alternatives are allowed in your area. It sounds like a 2 bedroom permit is certain, while a 3 or 4 bedroom system will require extra engineering and cost, if they are even allowed.
A conventional gravity system is always the cheapest to install and maintain. I would avoid exotic or novel designs wthout a proven track record.
You can also contact a licensed septic system designer, who can provide similar information. If the test results are on the fence, they would need to submit a design and see if it is approved. Sometimes modifications to the plan are required by the permitting authority. Stick with a local design firm who knows the town regulations and officials. They should know what will fly and what won’t.
You will need an approved septic system plan to get a building permit in most cases.
Paul Robert Hogg says
Old Perc Test Misleading
Absolutely great info. Without info such as above, we would of been in a pickle and out of pocket a lot of money. A real estate agent we were dealing with supplied us with a 17-year-old report which shower a high water table and a perc 2 soil. Our potential builder stated we could not have a crawl space or full basement as the water table was 40 inches.
Without the info from the agent and your info. Oh boy. Thanks you.
Allen H. says
Should I Re-Test With High Water Table?
I recently paid for a septic company to conduct a perc test on an undeveloped lot of property that I inherited in Calvert County, Maryland. I was not planning to build on the property – I intended to sell it. Yet my real estate agent said that interested buyers were asking if the property had a perc test before making an offer.
The property failed the test. The report.says that the property is unsuitable for sewage disposal purposes because “the groundwater is less than two feet below ground surface.’ It also says the applicable regulation is COMAR 26.04.02.05U(1)(a).
Because it failed the test, the Maryland Department of Assessment and Taxation sent me a notice that they’ve changed the value of the property from $45,400 to $8,900. They say I can appeal the notice within 45 days.
Another member of the community told me that the property is in a critical/flood prone area, yet there are houses on the properties on either side. I assume they have mound septic systems.
Is the test dependent on certain factors, like where the test is conducted on the property? Should I have the property re-tested and appeal the decision by the Dept. of Assessment and Taxation? What further steps should I take?
buildingadvisor says
Septic systems are governed by both state and local regulations and these vary widely, so it is hard to offer specific advice for your area. Maryland is one of the more stringent states, so you face an uphill battle. Local regulations can be more restrictive (but not less) than state regulations.
Most jurisdictions require 2 to 4 ft. of well-drained, native soil below the bottom of the drain field trenches for approval of a conventional septic system. That means that the seasonal high water table, as well as rock or hardpan, cannot be too close to the surface. The exact distance varies with local regulations.
In some cases, you can still install a mound system or other type of alternative septic system. The regulations can get pretty complex and so you will probably need some help in understanding how they apply to your lot.
It’s encouraging that houses on either side have approved systems, but their site conditions may be different or the regulations may have changed since their systems were permitted.
It’s possible that you can get different results on another part of the site, especially on a large lot with an area of higher elevation. On a flat lot, however, the distance to the water table is probably pretty consistent across the lot.
You can start by contacting your local health (or environmental) department to find out whether your site might qualify for an alternative system. Before retesting, I would get input from a local soils engineer or septic system designer who knows the conditions and regulations in your area. They can advise on the best strategy to move forward.
As for the tax assessment, it sounds like they have reclassified your lot as “unbuildable.” You’ll save on property taxes, but it sounds like you are concerned of the possible effect on the sales price or the buyer’s ability to get a loan. Buyers are much more concerned with the perc test results than the assessed value, so I wouldn’t worry about that.
Also, it’s doubtful that the tax assessor would raise the a value unless you can prove that the site is buildable. I can’t imagine they get many appeals to raise a property’s assessed value.
None says
You could always lie about the assessed value.
Hey, it worked for #44!
Scott Guroy says
I am talking with a lot owner about purchasing a 1.35 acre lot, which is vacant currently, but once had a modular home on it, and currently has a 1,000 gal septic tank in ground with a 300 ft. leach field. This home owner has not owned the property long, and does not have specific soil sample results from the property, nor does the county health department. Soil engineers in this area also seem to be pretty booked, and I am not able to get someone out to inspect the soil until mid/late July. Would you agree that it is a smart idea to move forward with the contract and title process, making the final sale contingent based on the soil sample results? The land owner and his wife do not seem to want to wait over a month for soil to be sampled for my peace of mind and records, but also say they are certain that the soil is buildable…. Do you have any suggestions on how to communicate this soil sample need before official purchase?
Keith says
Where To Perc Test On Large Lot?
I’m Looking to buy 47 acres of wooded land. Eventually I will want to build on it, possibly split it up into smaller lots and try to sell them down the road. Not sure exactly where on all this land I want to build my house yet. How do I choose where to do a perc test before buying to confirm the land percs and not have to do it again when I build?
buildingadvisor says
The short answer is that you have to do the perc test in the location of the drain field in order to get a septic system permit. So unless you have a specific house site in mind, it will be difficult to decide where to conduct a perc test. Even on fairly uniform terrain, there can be a lot of variation in soil permeability from one location to another.
If you’re not sure where you want to build, then you may need to test more than one location if you want to eliminate any uncertainty. Also, perc test results expire after 2-5 years in most locations, so you may need to retest or pay a fee to update the results when you are ready to build.
Planning to subdivide complicates things further. Assuming you can get permission to subdivide, you (or the future buyers) would need to do separate tests on each individual lot. Developers often do expensive engineering studies of land they are planning to buy and subdivide. Accessing potential test sites on a large, wooded parcel can be difficult and costly.
You should check with the local health department see if they have any perc test results on file for this parcel. Also, they can fill you in the requirements for perc testing, which can vary a great deal from one town to the next. Test procedures can range from simple and cheap to complex and expensive.
A licensed excavator or septic system designer in your area should be familiar with local soil conditions and may be able to provide some insight about perc testing in the area. Do most sites in the area easily pass the perc test, or do they often encounter dense soils, shallow water tables, ledge, or other difficult conditions?
Neighboring properties can offer clues. Do you see a lot of homes nearby with conventional septic systems or are mounds a common site in the area? Also, you are likely to get better test results on the higher and drier portions of the 47 acres, far away from surface water or natural drainage flows.
Still, you can never be 100% certain without conducting a perc test, so it’s usually the best way to proceed.
Yousif Abudra says
Can I Improve Soil To Pass Perc Test?
Is it possible to conduct slip plowing or deep ripping at a 3-6 foot depth in order to break past a clay layer that exists at 19 inches? I am wondering if I can do this 3-5 (or more) years before a perc test. How long does “disturbed” soil stay disturbed? How long can a trained eye tell soil has been “disturbed” for?
buildingadvisor says
All modern septic system codes require that perc tests be conducted on “undisturbed” soil. The drain field must also be placed on undisturbed soil.
For the purpose of septic systems, “undisturbed” soil has not been filled, compressed, or otherwise tampered with. There is no specific time period.
In foundation design, soil that has been filled or otherwise disturbed may tested by an engineer and certified to carry a certain load. In septic design, however, there is less flexibility. Soil can generally not be improved or rehabilitated for purposes of perc testing.
While anecdotally, you hear of people who have brought in many truckloads of fill and then waited five to ten years to pass a perc test, I don’t know any municipality or sanitary engineer who would knowingly approve of it. Also, there is no guarantee you will pass the test after waiting several years. For one thing, you need just the right mix of granular soil to pass. It cannot be too porous or too dense. Also in the intervening years, septic codes could become more stringent in your area. This is the general trend.
Many efforts have been made to cheat perc test results. However, if you manage to squeak by with perc test results that don’t accurately reflect the actual site conditions, you could end up with an underperforming septic system that fails prematurely. Also, if you certify that the soil is undisturbed, and it is found to be otherwise, you could face significant penalties.
Your time and money would be better spent hiring a local engineer or licensed septic-system designer. He can lay out your options, based on your site conditions and his knowledge of local regulations. What is acceptable varies a great deal from one town to the next, so you can’t make any assumptions. You can also reach out to the town’s health department (or whoever hands out septic system permits) and find out what alternatives are permitted in your area.
Often, a mound system is the cheapest alternative to a conventional drain field. On a sloped site, it is sometimes possible to operate a mound system on gravity alone. Other options include a pre-filter, such a sand filter to partially treat the effluent before reaching the drain field. On larger sites, you may find another location on the site that meets the requirements of a conventional system.
Sylvia Bae says
Can I Build 5 BR House With 4 BR Perc Test?
If the soil test comes out for 4 bedrooms but you want to do a 5 bedroom build, can it still be done?
buildingadvisor says
The short answer is no, the town does not think the site is suitable for a five-bedroom septic system, so they will not issue you a permit for a five-bedroom home. Some towns will allow you to build four bedrooms plus a “bonus” room (typically with no closets) depending on exactly how the town defines a bedroom. However misrepresenting the number of bedrooms could come back to bite you when you sell the house or need a septic system inspection at a future date – for example, when applying for a permit to remodel or add on.
It’s also possible that the town would grant you special permission for a five-bedroom house if you add components to your septic system that enhance the treatment – such a sand filter or other pretreatment system. This is a long-shot, but it never hurts to ask. Schedule an appointment with whoever issues septic system permits – typically the health or environmental department and see what options you may have.
Bob says
How To Interpret Perc Test Numbers
Had a Perc test done and the numbers they gave me was 1 and 5… what goes this mean?
buildingadvisor says
Perc test results are usually given in minutes per inch – that is how may minutes it takes for water in the saturated test hole to drop one inch.
The allowable rates for a conventional septic system vary from one municipality to another, but typically range from about 3 to 60 minutes per inch. At less than 3, the soil is deemed too permeable so that effluent draining from the leach field could potentially pollute the groundwater. Above 60 minutes, the soil is deemed too impermeable, so that it cannot absorb the effluent fast enough to effectively treat the sewage.
Less commonly the perc test results are given in inches per hour. In that case, the acceptable range is typically from 1 to 20 inches per hour. The math works like this:
60 min./in = 1 in./hr
3 min./in = 20 in./hr
Your numbers 1 and 5 most likely come from two test holes – the minimum number in most locales. If they represent minutes/inch, then your soil may be too permeable for a conventional septic system. If the results are given in inches per hour, then you might squeak by. In many areas, the worst performing test is the one that counts.
Best to check with your testing company for more detailed results. Then check with your town or county’s health department to find out the test limits for your area. Even if your site does not qualify for a conventional septic system, it may be suitable for an alternative system. Your health department can fill you in on the details and options.
Lisa Jalufka says
Can 2 Small Drainfields be Combined?
If a lot has two drainfield sites, and each perc’ed for 2 bedrooms, can the two sites be “combined” to allow a 4 bedroom house be built on this lot? It would be an alternative system from the information provided.
buildingadvisor says
That would be up to the local authorities who grant septic system permits – generally the health or environmental dept. If you’re not sure, check with your local dept. of building inspection. The rules can vary a great deal from one town to the next and, in some cases, the question falls into a gray area and is subject to the discretion of the individual enforcing the rules. Your’s could fall into that category.
If you are intending to direct the effluent from the tank to two separate drainage fields, maybe they would allow four bedrooms. If you are hoping to combine the two fields into one for four bedrooms, I doubt if they would allow that.
It’s best to arrange a face-to-face meeting with the permitting department ahead of time. Bring whatever documentation you have along with a site plan showing the footprint for the house and any other structures. Explain what you are trying to do and find out if you can work out an acceptable solution. If at all possible, get their opinion in writing. You may need this later if you are dealing with a different person when applying for the permit – or even the same one. Verbal agreements don’t hold much water when the official says, “I never said that.”
Best of luck!
Kay Johnson says
Can We Have High Water Table in Reserve Drainfield ?
We need to designate a reserve drainfield area and are told to god down 3 feet by two feet
Due to the high water table right now excessive rain – once we get down past the two feet we start getting some ground water, even though the current drainfield is in a lower area of the property
For the reserve area would this fail examination for a reserve ? Obviously testing during the summer or drier timeframe would produce different results. Our current septic drainfield is new and working fine we just need to move the reserve area to a new location due to building a shop garage.
buildingadvisor says
The same rules apply for both the primary drain field and the reserve area. Both must pass the perc test and whatever other tests are required by your area. Typically this includes a “deep hole” test to examine the soil and determine whether the seasonal high water table or a layer of impermeable soil (or rock) is too close to the ground surface for a conventional drain field. Typically, they want to see three feet of well-drained soil below the bottom of the trenches before hitting water or hardpan.
Some jurisdictions limit when these tests can be done, so they can observe the site under worst-case conditions, such as the springtime or rainy season. Others allow testing any time and use observation of “mottling’ in the soil to establish the seasonal high water table.
Typically, but not always, it is drier on the higher portion of a property. Water tables don’t always follow the surface contour of the land.
Your fist step should be to contact the health department in your area to find out what testing is required for a reserve field, who can do this, and when. Get a septic system designer out to the property to help you locate the more promising location for a reserve field.
If none can be found, the town may allow you to designate the original field as the reserve field. This requires a very messy job when it is time to replace, but may allow you to move ahead with your project.
A.C. says
Where Can I Find Perc Test Results?
How do I find out if a lot I am considering passed the perc test? I am in South Carolina.
buildingadvisor says
Perc test regulations vary a great deal from one town to the next. This includes how to conduct the test, when it is allowed, how can perform it, and how long the results are valid – typically 2 to 5 years. In some cases, the results can be updated for a fee.
In most areas, the testing and permitting is handled by the town or county health dept. or dept. of environment/conservation. If you’re not sure, check with the dept. of building inspection and they can point you in the right direction.
If a valid test was performed, the results should have been recorded by the health or conservation dept. In some cases, a septic design was also approved. Always check with the health dept. before proceeding. Don’t make any assumptions.
I would start by asking the seller or seller’s representative if and when a perc test was performed and whether they have the test results. But always confirm the information with the permitting authority. If they don’t have a record of the test, then the site will probably need retesting. But you will have some idea of whether the lot is suitable for a conventional or alternative septic system.
Christine Stanley says
What’s The Cost of a Perc Test?
I paid 500.00 dollars for a soil scientist to perform a perc test. He only dug two small holes and failed the spot we wanted to build on. So my husband dug additional holes later, according to the advice of the soil scientist. The water he put in the holes disappeared quickly the way it should. Now the scientist wants $1,600 additional dollars to come and certify the test. Is this right or our we being taken advantage of?
buildingadvisor says
Like everything else in life, the “average” cost may not reflect the actual cost in your situation.
In general, standard perc tests costs in the range of $300 to $500 in lower-cost areas like the Midwest, and closer to $1,000 in high-cost areas like the West Coast or New England.
If a deep-hole test is required, you may end up spending in the range of $1,000 to $2,000 for the complete test, including the cost of the excavator. A lot depends on the number of holes or trenches required.
The charge of $1,600 to certify your test sounds very high to me. I would definitely make a couple of calls to other professionals who are certified to conduct perc tests in your area. These might be a soil scientists, sanitary engineer, or licensed septic system designer.
You can contact your local health department or department of building inspection to find out who is authorized to conduct a perc test. They might also have a list of local professionals who are qualified to perform tests.
Best of luck!
Darlene Nicholas says
Why Do I Need A Sand System?
I have a small house with an older cinder-block septic tank. It has not given me any trouble but now I need to sell. I had a soil test done and the tester said it was fine and that I could put a cheap conventional system. However, the county came back and said no I need a sand system. That’s $5,000 more. Whats’s up? Help!
buildingadvisor says
The town or county, or whoever has jurisdiction (sometimes the state) makes the rules and the rules change over time.
It sounds like your site did not pass the perc test for a conventional septic system and the country wants you to put in a sand filter – probably as a pre-filter for your leach field.
In addition to the extra initial cost, you will probably also need a pump, controls, and alarm to dose the sand filter – all of which adds ongoing maintenance costs to keep the sand filter operating properly.
As a first step, I would contact the county health department or DEQ (whoever hands out septic system permits) and get clarification on exactly why you need a sand filter and whether there are any simpler alternatives. A licensed septic system designer can help you figure out what is the best option in terms of initial cost and ongoing maintenance.
You can read more on Sand Filters at this link.
Best of luck in dealing with the county – never a fun experience!
Maxine says
Can Septic System Go On Lot Next Door?
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I just recently purchased two lots. I wasn’t sure if one lot would perk so I bought the other lot and, just as I thought, one of the lot perks and the other does not. Can I still put a septic system down on the lot that perked in NC?
buildingadvisor says
Assuming that the lot is zoned properly for the building type and size you want, then you can certainly build on the lot that perked.
If you want to build on the other site instead, you can usually find a way to accomplish this. Often the simplest solution, if the two lots are touching, is to combine them into a single lot – if that’s what you want.
If the two lots are not touching, and your sewage line has to cross someone else’s property, then you will need to acquire a sewer easement to run your piping across their land. There is no guarantee they will agree to this, but sometimes money can be a motivator.
Finally, if you want to develop both lots separately and use this as a shared septic system, that is often an option as well.
At the end of the day, it up to your local septic system regulations and the officials who interpret and enforce them. It’s always best to do your homework first and then meet with them face to face, with all the relevant information at hand and all your ducks in a row. Your knowledge of the local regulations will help you present a stronger case.
If you learn that you will need a variance or special permit to achieve your goals, you may want to hire a real estate lawyer and septic system designer. But with one lot that perks, you should have a lot of options.
Read more on Zoning
Valerie Tarkenton says
County Will Not Permit Septic System Repairs
We have kept up septic maintenance since buying our home in 1999 and in many cases have had our tanked pumped more often due to problems we continue to have with a price tag of $2,500.00 each time Most recently, we were told our lines needed replacement. Ok. We proceed to start the process only to be told the soil samples came back and according to the results our soil cannot sustain a septic system and the county cannot issue the permit. Every home within this neighborhood has and continues to have the same problems we do with their system. We are the first however to try and replace the lines. I realize many things can change the top layers of soil, however, going deeper to where the system is, I would think it would take a lot more then my lifetime to encounter this soil problem. Has anyone else encountered similar problems, and if so, please share your outcome. We were informed the county should not have authorized a permit for a septic system to begin with.
buildingadvisor says
I can’t tell from your posting exactly what the problem is, but it sounds like your drain field (leach field) has failed. This happens eventually to all drain fields as the soil get clogged over time with solids and grease from the effluent. Failure can also result from the formation of a think slimy layer called the “biomat” that interferes with absorption. This is caused by overloading of the leach field, due to too much water and/or too much organic waste.
In your case, it sounds like the problem is compounded by poor native soil that is too dense to absorb the water from your septic system. This is often due to high clay content. Because of the slow drainage, the system is backing up, making frequent pumping necessary. The absorption capacity of the soil is typically measured by a perc test.
The most common sign of a failed drain field is a soggy, smelly area over the field where effluent has come to the surface. The septic tank will also fill quickly to capacity and, if not pumped out, the house drains will back up.
In some cases, a partially clogged drain field can be rehabilitated, but the only reliable approach is to wait a few years for the soil to recover on its own. If the soil was never suitable for a conventional drain field, then you will need to explore the feasibility of alternative systems.
I am surprised that your county health department is not more cooperative in helping you find a workable solution. I suggest that you contact a licensed septic system designer or soils engineer who works in your area. They may have better luck in dealing with the local authorities and can help you plan and install an alternative septic system that is acceptable to them.
Until you solve your problem, you should do all you can to can reduce the loading of the septic system. Use water-conserving appliances and fixtures, space out use of the washing machine, avoid use of disposals, and don’t pour any harsh chemicals down the drain. Make sure drainage from the yard, roof, or sump pumps does not collect over the field.
Best of luck in finding a workable solution.
A.H. says
As I’ve been looking into the design of our wastewater treatment solution, I’ve learned a bit about aerobic treatment systems. Now I’m not a professional by any means, but from what I’ve seen, you’ll spend less than one pumping, create a healthier treatment system that drains better, and won’t have to pump nearly as often. I would definitely explore this option. And if you have already come up with a solution, I’m curious to know what you decided on.
GinaC says
Should Buyer Pay for Perc Test?
Hello, I’m looking at a piece of land that has been used as a campsite. It has had no perc tests done and has no well. Houses on adjacent lots in the same area have working septics and wells.
The realtor would like me to get a perc test done and have the offer contingent upon passing it, which I would be fine with. He said that I do not have to worry about finding water, but I would also like a contingency for a well, even though I do not plan to build soon.
But what is stopping the seller from using me to pay for a perc test, refusing my offer, and then jacking up the price since the perc test will then be on record?
buildingadvisor says
Sounds like your real estate agent is representing you as a “buyer’s broker”. If that’s the case, your agent can help you draft a binding offer that is contingent on a successful perc test. You can also have a real estate lawyer review your offer if you want an independent legal review.
If the contingency is written properly and the perc test is successful, then the seller is legally obligated to sell you the lot under the terms and price specified in the purchase and sales agreement.
Often you can get the seller to share the cost of the perc test. It all depends on the market conditions and the overall strength of your offer. Like everything else in real estate, who pays for the test is a matter of negotiation.
Read more on adding contingencies to your offer.
Best of luck with your purchase!
Debra says
Uses For Land That Does Not Perc?
I’m looking at a property that may not perk. Assuming it doesn’t, is it possible to have a well put down and power company run power to the property!!
I would be using it to store Conex storage containers on. I plan to keep one camper there at all times, and then occasionally have one or two other campers come in for a short period of time. All campers would be using a dump station.
Does this sound like something that would normally pass???
buildingadvisor says
Assuming that you do not have access to a municipal sewer, then a perc test is required to build a house or a commercial building with plumbing.
Depending on the zoning, land that does not perc is often used for farming, logging, or recreational purposes such as hunting and camping. You may also use it for storage, as you have in mind, if permitted by zoning. A garage, barn, or other storage building might also be allowed.
Whether the local authorities will allow you to bring in power and water, and keep a camper on the site, is hard to say. This type of use will be governed by the local zoning rules and how they are interpreted by the officials with jurisdiction. Your intended use may fall into a gray area, so you will need to get input both the health department and department of building and zoning.
If at all possible, get their opinions in writing, so you will have documentation if a few years from now a new town officials question your use of the land. This can happen if you decide to sell, build, or otherwise require a permit for some type of work or change of use.
Best of luck!
Christy says
Is 60 Minute Perc Test Acceptable?
The perc test received on a piece of property says the rate is 60 minutes per inch. How does this help me determine the number of bedrooms I could build? What is an acceptable rate?
buildingadvisor says
Most jurisdictions have a maximum rate of 60 minutes per inch (mpi) for a conventional septic system. For some areas, the maximum rate is 30 mpi. You can check your local regulations online or contact the local agency in charge of septic system regulations – usually the health department or department of environmental quality. Higher numbers generally indicate dense soils with higher clay content that do not readily absorb water.
The percolation rate determines the size of the leach field required, so a site with a higher number (slower drainage) will require a larger leach field for a given number of bedrooms. Designers assume two occupants for each bedroom in their calculations.
If your perc test results are over the acceptable limit, you may still be allowed to build a mound system or other type of alternative septic system.
The number of bedrooms allowed is usually determined by zoning or subdivision regulations, not by the perc test, although the perc test can play a role on a small lot if the required leach field size cannot fit on the lot with proper clearances. In some cases, the number of bedrooms allowed is “grandfathered” based on the regulations in place when the lot was originally subdivided.
It’s best to check with your local zoning official before proceeding with building plans as the allowable number of bedrooms is not always crystal clear.
Best of luck with your building project!
Rebecca says
Regulations For Adding Bedrooms Are Confusing
We are trying to add two bedrooms and one bathroom to our home. We currently have a 2 bedroom, 1 bath home. We have 5 people in the house now so we NEED more space. The health dept. of environmental services says the home percs for 2 bedroom. She said if we had 4 people in the home instead of 5, she could approve a certain type of permit to allow six people to live in the home BUT because we exceed the 2 people per room “law”, she cannot approve a permit. This makes no sense to me. She said to go ahead and have a soil test done anyway, though. Is that necessary when we already know the house percs for 2 bedroom? Would it possibly make a difference?
Any info would be greatly appreciated!
buildingadvisor says
Sure sounds confusing. Zoning and septic regulations are all created and enforced at the local level, and there is a lot of variation from one jurisdiction to the next, so it is hard for me to say what is allowable in your area.
There are often workarounds, loopholes, and gray areas that are subject to interpretation by local authorities. It sounds like this person is trying to find a way for you to move ahead with your project, but is confusing you (and me) in the process.
The general assumption in septic system design and permitting is two people per bedroom. So a two bedroom system is designed for 4 people. A four bedroom system is designed for 8 people. It sounds like the health department has some way to allow up to six people to use your current system – or a new larger system – but cannot issue a permit for the extra bedrooms. She may want you to do a new soil and perc test because the old test has expired – or she may be hoping that you get slightly different results this time – not really sure.
Also it is not clear whether she wants you to use your current septic system, as is, modify it in some way, or build a completely new, enlarged system.
Also if she cannot approve the permit for the extra bedrooms, what’s the point? You will need to ask her for clarification. For best results, schedule a face-to-face meeting with the health dept. to untangle this. Bring someone else to the meeting who is familiar with construction and permitting so you have a second pair of eyes and ears.
Finally, even if you are allowed to add a fifth person to your current 2-bedroom system, you should be aware that this will increase the load and possibly shorten the life of the system. It would be wise to pump the system more frequently and to treat the system gingerly: use low-flow faucets and fixtures, avoid putting any products down the drain, avoid drain cleaners and other harsh chemicals.
Avoid putting the following down the drain (list courtesy of Flowhawks.com)
• Egg shells, coffee grounds, nut shells
• Meat scraps, fats, grease
• Sanitary napkins, tampons
• Disposable diapers
• Paper towels
• Paints, thinner, chemicals
Tom says
DIY Perc Test Procedure
I would like to perform my own perc test rather than hiring a professional. I’ve done some preliminary testing, and I may have too fast of a percolation rate.
My methodology was as follows:
I dug a hole 6″ in diameter and 24″ deep. I then filled it with water and started measuring immediately. I refilled the hole whenever it was down about 8″. I continued the measurements for 42 minutes. The initial rate was about 100 inches/hr, probably due to lack of soil saturation. The final rate was 13.5 inches/hr.
My questions:
1. Did I continue the test long enough (42 minutes) for the soil to reach saturation?
2. Would the test be more accurate if I inserted a 4″ drain pipe into the hole, thereby preventing water from permeating the sides of the hole?
3. What would be considered too fast for a conventional system?
4. Are there systems available that are engineered to reduce the rate of absorption?
5. If so, how much might I expect to pay for such an engineered system?
6. Did I provide enough information for you to answer the above questions?
Thanks for your guidance!
buildingadvisor says
I recommend that you contact your local town or health department (or whoever oversees septic system regulations in your area) to find out what procedure is recommended or required in your area. Your test hole seems about right – it should be equal to the depth of your leach field trenches. A minimum of two or three holes are typically tested.
Except in highly porous sand and gravel soil, you are generally supposed to saturate the soil for a minimum of four hours and preferably overnight. In most cases, the perc test is conducted the next day. Sounds like you may not have adequately saturated the soil prior to measuring the absorption rate.
Typically each hole is filled to 6 inches above a 2-inch layer of clean gravel at the bottom. Some technicians measure the time it takes for the water level to drop to 5 inches and then refill to 6 inches. Others take a precise measurement about every 30 minutes and refill then. In either case, measurements are taken until two consecutive measurements are approximately equal, indicating that the rate has stabilized.
The worst performing hole is used to determine the rate. A final rate of 13.5 minutes per inch (MPI) indicates a well-drained soil well suited for a conventional leach field.
If you do require an engineered “alternative” septic system, you can expect your costs to be at least twice the cost of a conventional system. Which system would work best for you would depend on local conditions and what systems are accepted by local authorities. The least expensive system with the fewest moving parts is usually the best choice.
Typical perc test procedures are described at this link.
Nicole says
Excavator Needed for Perc Test?
What size compact Excavators is needed to complete a perc test? We need to rent one but are unsure what to get.
buildingadvisor says
Procedures vary a lot by jurisdiction, but most perc test holes are pretty small. They are typically about a foot in diameter and should be dug to the depth of the proposed absorption trenches, usually 2 to 3 feet. Two or three holes are typically dug using a post hole digger or power auger on a small excavator. Any compact excavator such as Bobcat or skid steer can work with the right attachment.
The deep observation hole, required in many areas, usually requires a hole of 7 feet or more – large enough for a worker to safely climb into. One side is usually sloped for safe access. Most small excavators with the right attachment can handle this, but the bigger the equipment the faster the work will go. Around here, a small to mid-size backhoe is often used.
Best of luck with your perc test and building project!
Emily Baird says
Marginal Perc Test Results
What is the difference between a marginal perc site and a regular perc site? Also, have you ever heard of the soil test determining the size of your home, not in terms of bedroom but square feet?
buildingadvisor says
Although you can “pass” some college courses with a D, you may not want to hire the college graduate with barely passable grades. Similarly, I would be cautious about a site with marginal perc test results.
The term “marginal” is sometimes applied to soils and sites that either just passed or just failed the perc test – indicating that a larger leach field or alternative system may be required for adequate performance. Alternative systems are a lot more expensive to install and maintain than conventional systems. Also a system installed in marginal conditions may be more prone to problems.
While perc testing is based on science, the actual tests are governed by somewhat arbitrary rules that vary from town to town, as well as visual observations of soil characteristics (like mottling) which are somewhat subjective. For example, some towns require testing during the wet season, while other allow testing year-round. A site that just passed during very dry weather might flunk during a wet spring when the soil is saturated and the water table higher. Yet the septic system must perform under all weather conditions. Some towns require an engineer or town official on hand; others do not.
Sellers have a strong incentive for a site to pass. In areas with less rigorous test procedures, it’s possible that someone could skew the test results of a marginal site into a passing grade in order to make a lot marketable.
Regarding your second question, no, I have never heard of a soil test limiting the size of a home. In general a septic system is designed for a number of bedrooms, with the assumption that each bedroom will have up to two occupants. What exactly counts as a bedroom does vary from town to town. Some towns are pretty loose in their definition; others are very strict and will not let you build any extra “bonus” rooms or other finished spaces that could be used (or easily converted) to a bedroom.
It’s also possible that the size and location of the required leach field and replacement field, along with property setbacks and other zoning regulations, may leave a buildable area too small for the house you have in mind.
Samantha says
Choose House Site Before Perc Test
We recently purchased land and had a perc test performed. We live in Menifee, Ca. When we went to mark where we wanted or home placed, we were told it could not be possible because the perc test markers are there. Is this accurate? If so, I do not understand why the company would not ask me where we wanted to place our home before performing the test. Any advice?
buildingadvisor says
Typically, the approximate house site, well location (if needed), and leach field area are planned in advance of conducting a perc test. It’s hard to say why the testing company did not discuss these issues with you and chose that particular spot.
Sometimes, there are limited options for siting the house and septic system due to the required setbacks and clearances, and to the location of suitable soils and site conditions, including slope, surface water, and depth of the water table and ledge or impermeable soils. Septic systems have to be a certain distance from the house, well, property lines, water lines, streams, etc. Some towns require both primary leach field and a designated replacement field.
It may be that this was the only suitable spot for a leach field. Or it’s possible that your tester jumped the gun and picked the spot based on easy access or incorrect assumptions about your building plans. In any case, they should have discussed the site plan with you ahead of any testing.
I would suggest contacting the local health department (or dept. of building inspection), which typically oversees septic testing and permitting. If you find out that you have other options for locating the septic system, then get back in touch with the testing company. Hopefully, they will cooperate and re-test, if necessary, in the proper location.
Best of luck with your new home!
David Gelhausen says
Is Perc Test Transferable to Buyer?
I am looking to purchase a lot in Ohio. The current owner had a perc test done and passed. Can that same test be transferred to me?
buildingadvisor says
In general, perc tests run with the land, not the owner. So the test should be transferrable as long it was properly done and has not expired. Depending on the local regulations, test results may be valid for one to five years or more, and in some cases can be renewed for a fee.
A perc test, however, is not the same as a permit to install a septic system. This takes into account other factors such as lot size, setbacks, site drainage, and the number of bedrooms. Building permits and septic permits are generally not transferrable.
In some towns, the perc test results need to be reported to the local health department and are a matter of public record available to you upon request. In all cases, the test would need to be done in accordance with local law to be valid.
Since rules vary so much from town to town, it’s best to not make any assumptions. Make any offer contingent on your review and approval of the perc test results. If your offer is accepted, contact the local health department or department of building inspection to confirm that the lot is suitable for the building you have in mind.
You can also contact a local septic system design firm for help if you cannot get clear answers from the town or county. Best of luck with your lot purchase!
Eddie says
Why Do I Need Perc Test for Addition?
I am building addition on my house. We are adding no more plumbing to house.
We are redoing both bathrooms that are already in home. Now the county is saying I need a wet season perc test and I may have enlarge my septic tank. The 1,000-gallon septic system that is there now works great. This does not make sense to me. HELP!!
Thanks Eddie
buildingadvisor says
Sorry to hear about your situation – it’s a tough one that I have had to deal with a couple of times. Septic system regulation is a very local affair and the governing jurisdiction (town/city/county) has a lot of discretion in making the rules as long as they are in compliance with state law. In general, local rules can be more strict than state rules, but not less.
Some local jurisdictions have started requiring a septic inspection, under certain conditions, whenever you sell or remodel a home — even if you are not adding a bedroom. In some cases, you may be required to bring your system under current code even it complied with the code when installed.
If you are adding a bedroom, or a room that the county considers a bedroom, then a septic system upgrade is almost always required. System size is determined by the number of bedrooms, not bathrooms.
If you or any previous owner added a bedroom (or converted an existing space to use as a bedroom), that could also trigger an inspection and upgrade requirement.
When you go to get a building permit or wish to transfer the deed to a new owner, the town has the leverage to say “Not until you get your septic system inspected and upgraded if necessary.” At this point they have you over a barrel.
You can try to fight it, but it is difficult to prevail. Some people do the construction work without a permit, but that carries big risks. You can be fined and, in the worst cases, forced to undo the work you’ve done.
The place to start is by meeting with your county health dept. or whoever oversees septic regulations in your area. Ask why a new test is required at this time and why a larger tank might be needed. With this information, you may be able to find a less expensive workaround.
Bill Cranshaw says
Does Drought Help Perc Test?
Does the current drought conditions help/hurt the perc outcome? Boston, MA area
buildingadvisor says
Parched ground will certainly drain faster (perc better) than ground that has a high moisture content. For that reason, and to avoid frozen soil, many towns limit perc tests to the wetter or warmer months of the year. In any case, most towns require that the test hole be saturated with water for a number of hours before the test. The purpose is to create worst-case conditions since the septic system is expected to perform well in both dry and wet weather. In addition to the pass-fail criteria, the perc test determines the required size of the leach field.
Drought conditions also lower the water table, which is usually assessed by a “deep hole” test conducted along with the perc test. Technicians look for mottling in the soil to visually determine the seasonal high water table, so the actual conditions the day of the test are not that important. Of course, a test hole that fills with water is not a promising sign for permitting a conventional leach field (although an alternative system might still be allowed).
If you game the system somehow and get better results than warranted by the soil conditions, then you could end up with a septic system that fails due to an undersized leach field or one that pollutes the groundwater in wet weather – not a good outcome for anyone.
manny singh says
Cost of Perc Test?
What is the cost of a percolation test, including a 15 ft. deep-hole test, and filing the results with building department. How much would the total cost be?
buildingadvisor says
It is hard to generalize as the testing procedures, number of test holes, and fees associated with obtaining a septic permit vary a great deal from one town or city to the next. Also sites with difficult access or difficult digging with shallow rock or dense clay will be more expensive. In some rural areas, all you need a shovel, a bucket of water, and a watch. In more heavily regulated areas, you may need a licensed technician, an observer from the town, and a backhoe. If you are digging a 15 ft. pit, you clearly need a services of an excavator.
The average cost for a perc test ranges from $300 to $700, or closer to $1,000 if an excavator is needed. If a deep-hole test or is also required, the total cost is more likely to range from $1,000 to $2,000. Always better to estimate high and be pleasantly surprised if costs come in lower.
Best of luck with your project!
megen says
5BR House on 3BR Lot
We are interested in building a five-bedroom house in middle TN to accommodate our growing family. There is an auction coming up with land that would be the perfect location for us. However it says it has perked for a three-bedroom house. I have read you can just build whatever you want, but it would be considered a three-bedroom. My issue with that would be the potential for problems down the road if we still have six people living there. Is it possible they didn’t test to see if it would accommodate a bigger house or would there be anything we could do to be sure we wouldn’t have any problems if we were to buy and build on this property?
buildingadvisor says
The maximum number of bedrooms is not determined by the perc test, but by zoning regulations. This is usually governed by the size of the lot, the zoning district, and a host of rules each community develops to regulate growth. If the lot is approved for a three-bedroom house, you cannot legally build more than three bedrooms.
The perc test determines whether or not you can install a septic system on the property. The results of the test are also used in designing the leach field. The septic system is designed for a certain number of bedrooms, with the assumption that each bedroom may have up to two occupants. So a three-person septic system should be OK for up to six people. However, with that level of usage, you will need to pump out the tank more frequently than with two or three occupants in the home and the leach field may not last as long.
If you want to build more than three bedrooms, you may run into problems in permitting, or when you renovate or sell the house. Exactly what a town considers a bedroom is highly variable. Some people get around the limit by naming their extra rooms a “bonus room”, media room, home office, etc. Or they finish a room in the attic or basement after they have been issued their occupancy permit. Some municipalities are strict and any room with a standard doorway and a closet will be considered a bedroom. Other towns are a lot more lenient in this area. It really depends on the policies of the town and, in some cases, on the opinion of the individual building inspector or zoning officer.
You can discuss this with town officials beforehand, or you may be surprised when you submit your house for a building permit and are told that your plan needs to be modified.
Best of luck with your new home!
William Barbour says
Will My Soil Type Perc?
Hi, I am looking at buying 13 acres in my home town of Turkey North Carolina. A perc test has never been done on the land and after doing some research I found the land to be Rainy Loamy Sand(RA) and the other half of the land being Goldsboro Loamy Sand (GoA). I found that RA is pretty much a no-no for anything so we are going to build a fishing hole there if we get the land. GoA is found to be “Moderately Well Drained”. My question is what do I need to look at to get an even better idea if the GoA part will pass perc before shelling out the cash to go through with it? Some things are just confusing me and we are running out of time to make an offer on the land. Thank you!
buildingadvisor says
Goldsboro Loamy Sand, as you have already discovered, is classified as “moderately well-drained and moderately permeable” soil type. Loamy sand falls somewhere in the middle of soil absorption capacity (see Table 2.6). In general, that bodes pretty well for passing a perc test, as long as you don’t have other problems such as a high seasonal water table or rock/hardpan too close to the surface. In that case, you could still probably get a mound system approved. The required absorption rate to pass a perc test varies with local regulations, so you really need to consult with local experts.
In general, you want a well-drained, sandy soil for a leach field. A typical loam is 40% sand, 40% silt, and 20% clay, but these percentages can vary a great deal depending on the specific soil type – there are over 12,000 soil types identified in the US. Too much clay in the soil slows down absorption, which can lead to a failed perc test. Too much course sand or gravel (a much less common problem) can flunk the test by draining too fast, potentially threatening the aquifer.
Short of paying for a deep-hole and perc test, you might have some luck talking to local companies that design septic systems. They should be familiar with local soil types and local regulations and may be willing to provide some insight about your building site. They might be reluctant, however, to give an off-the-cuff opinion for fear of being sued if they turn out to be wrong.
Short of conducting a full test, you might also have luck getting someone to do a 3” test bore to take a look at a soil sample. This should give a soils scientist enough info to tell you whether the site is likely to be suitable for a conventional leach field.
Perc testing is typically done by an engineer (civil, soils, sanitary, or geotechnical), or in some areas by a licensed septic system designer. Some jurisdictions allow owners to do their own perc tests. Contact the local government agency that oversees septic system permits for specific information. If you’re not sure who to call, start with the department of building inspection, who will refer you to the proper folks – usually the dept. of health.
Angela says
Do Large Lots Require Perc Test?
If you own ten acres do you need a perc test?
buildingadvisor says
The answer to your question depends on state and local regulations. Your best bet is to contact the department that oversees septic permits in you area, typically the dept. of health, sanitation, or building inspection. They will be able to tell you who needs a perc test, who can perform it, what time of year, etc.
In our state, Vermont, most properties of 10 acres or more are exempt from perc tests under state law. But you will still need a perc test, or at least a deep hole test to examine soil types and seasonal water tables, in order to design a proper septic system. If the site is not suitable for a conventional leach field, then it will not work well and you may end up with backed-up pluming and a soggy leach field with potential health risks.
Bottom line: You may want to conduct a perc test even if it is not required by law in your area.
Mike says
After Failed Perc, Can I Try Second Location?
I own a 3.5 acre lot that sits on a hill and is nearly all wooded. It failed a perc test before I purchased it. Is it possible for it to perc somewhere else on the property?
buildingadvisor says
It is possible that you could pass the test in a different location or another time of year when the weather is drier. However, some municipalities restrict the time of year when perc tests can be performed. The logic is that you want to design a system that will work in all weather, not just in the dry season.
The perc test needs to be performed where the leach field will be located and is used, along with the number of bedrooms, to determine the size of the leach field. In addition, the type of soil and seasonal water table are determined by observing the soil in a deep hole test. This determines how much sand or gravel needs to be brought in to keep the trenches a safe distance above the water table or impermeable soils.
If the site has more than one suitable building site, then it may be worth testing in another location. A licensed septic system designer or engineer (civil or sanitary) could help you identify the most suitable sites. Your municipal building department or board of health can provide you with names.
If the site cannot pass the test for a conventional septic system, it is still possible that a more expensive alternative system would be approved. The most common is “mound system” where enough granular fill is brought in to create a raised leach field. A septic system engineer can help you evaluate your options and the associated costs.
Wilson says
Land Failed Perc Test for Years; Suddenly Passed
A building lot we are considering has failed perk tests for over 35 years but suddenly passes a perk test. How is this possible?
buildingadvisor says
Assuming the soil in the area has not been removed and replaced, the biggest variables are the water table and moisture content of the soil. For example, a site may fail in the rainy season (or after the snow melts) but pass in drier weather. Also one part of a site may fail while another will pass since soil and groundwater conditions can vary a great deal within the same lot.
The perc test itself varies from a pretty formal test conducted by a soils engineer to a guy with a bucket and a wristwatch – depending on the requirements of your local government. So some tests are more accurate than others.
I can’t say why this particular site would suddenly pass suddenly after 35 years of failure. Did it pass by a good margin or just squeak by? If I were buying this lot, I would definitely want a repeat test and would get the opinion of a septic system designer or soils engineer. In addition to a perc test, most cities and towns also require a deep hole test to examine the soil type and seasonal high water table. I would want a complete picture of the soil’s capacity to process sewage by an authorized inspector, and assurances from the town that the lot is buildable, before proceeding.
me says
Who Can Perform a Perc Test?
Who do I call to have a perk test done? There is no way I can do that myself.
buildingadvisor says
In some areas, you can legally perform the test yourself; others require that the tester is licensed by the state (usually by the Health Dept. or Dept. of Environmental Quality – DEQ). Some jurisdictions require that a town official witness the test. Check with the your local building inspector or health department to see what is required in your area and to get names of qualified inspectors. These might be engineers, septic system designers/installers, or other building professionals. In addition, you may need to hire an excavator to dig the holes for the perk test and deep hole test, if one is required.
Linda says
How Long is Perc Test Valid?
I am buying 8.8 acres with lakefront in Willow Ak. A perc test was done 8/97 showing less than 30 min per inch. Should this test be done again or should it be ok?
buildingadvisor says
Most likely, your perc test results will not change much over time, but the test results may no longer be valid. In jurisdictions that require perc testing before building, test results are typically valid for only two to five years, depending on local law. Some towns allow older test results to be renewed for a fee, subject to various restrictions. In addition to a perc test, most communities require a deep-hole test to examine the soil types and locate the seasonal high water table. While successful results are necessary to get a building permit in most places, they are also used to size the leach field. So you may want to do a new test whether or not it is required by local authorities.
Bill says
Do I Need New Perc Test Before Selling?
We bought 6.82 acres wooded land in 2000. The previous sellers had provided us the perc test that was done in 1996. Now we want to sell the land. Do we need to obtain the soil test again? Please advise.
buildingadvisor says
In most localities, perc tests don’t last forever, but how long they are valid is up to the municipal government (town/city/county) with jurisdiction over the lot. As stated above, test results are usually valid for two to five years. In many places, perc tests can be “updated” for a fee without doing additional testing. Check with your local building department (or health department or DEQ in some locales).
While you do not need to have current perc test results to sell a lot in most places, it will certainly make the lot easier to sell and potentially more valuable.
Joe says
Passed Perc Test, But Failed Deep-Hole Test
I did my perc hole tests last week and had great results so this week I hired an engineer and a contractor to perform the deep hole test. We hit clay at around 3 ft. and when we got to 6 ft. there was a presence of water. My engineer told me that I would not get a BOHA (Board of Health Approval) with these results in Westchester County NY. is there anything I can do to get approved?
buildingadvisor says
As you probably know, septic system regulations are governed at the town or county level, sometimes with overriding state laws. There is enormous variation, so I can’t comment on the particular laws in your jurisdiction.
In many areas, a site that fails for a conventional system may still be suitable for an “alternative” septic system. The most common type is a mound system which essentially raises the ground level at the leach field with suitable soils to provide the required clearances. A mound system can add $10,000 or more to the cost of your system and requires monitoring and annual maintenance, but is a proven system that is widely used. A wide variety of other systems are out there, but tend to be more complicated and less likely to be approved locally.
See Also: Are Alternative Septic Systems Allowed?
There is also the possibility that another area on your site would pass the deep hole test – if you have more than one possible locations for your leach field.
Your best bet, at this point, is to meet in person with the building and/or health department that has jurisdiction. Bring your test results and ask what options you might have to build on the site. In my experience these people are knowledgeable and helpful if approached as a resource prior to building.
If you are unable to get anywhere with local officials, a good real estate or construction lawyer in your area would be your last resort. It is possible that a “hardship” variance could be granted allowing you to build on the site despite your test results.
buildingadvisor says
Assuming the soil in the area has not been removed and replaced, the biggest variables are the water table and moisture content of the soil. For example, a site may fail in the rainy season (or after the snow melts) but pass in drier weather. Also one part of a site may fail while another will pass since soil and groundwater conditions can vary a great deal within the same lot.
The perc test itself varies from a pretty formal test conducted by a soils engineer to a guy with a bucket and a wristwatch – depending on the requirements of your local government. So some tests are more accurate than others.
I can’t say why this particular site would suddenly pass suddenly after 35 years of failure. Did it pass by a good margin or just squeak by? If I were buying this lot, I would definitely want a repeat test and would get the opinion of a septic system designer or soils engineer. In addition to a perc test, most cities and towns also require a deep hole test to examine the soil type and seasonal high water table. I would want a complete picture of the soil’s capacity to process sewage by an authorized inspector, and assurances from the town that the lot is buildable, before proceeding.
Jim Nosek says
Who Pays for Perc Test, Seller of Buyer?
Looking at 40 acres in Northern Arizona. Is the perc testing the seller’s responsibility or is that in the negotiation price for the land?
buildingadvisor says
Who pays for the perc test and deep hole test is a matter of negotiation. The specifics of the test – how it is done, who must do it, time of year, and so on – vary greatly from one location to another, so make sure you check with the local authorities (typically the health and/or building department) on what is required in your area.
I would definitely make any offer to purchase contingent on the lot passing a perc test. If the seller refuses to sell on that basis, it would probably be wise to walk away.
buildingadvisor says
In most localities, perc tests don’t last forever, but how long they are valid is up to the municipal government (town/city/county) with jurisdiction over the lot. Test results are usually valid for two to five years, depending on local regulations. In many places, perc tests can be “updated” for a fee without doing additional testing. Check with your local building department (or health department or DEQ in some locales).
While you do not need to have current perc test results to sell a lot in most places, it will certainly make the lot easier to sell and potentially more valuable.
Bob Frazier says
Right Temperature For Perc Test
Does the temperature have to be within a certain range for a perc test?
buildingadvisor says
When and who can perform a perc test can is governed by local regulations, so it’s always best to check with the building or health department in the municipality (town, county, or city) that has jurisdiction. During cold winter weather, the ground may be frozen deeply, which could effect the results since frozen soil will not absorb water without the proper precautions. During the wettest time of the year, the a high water table can be an issue. In addition to town officials, septic system designers, installers, and inspectors can be good sources of insight into local conditions and regulations. See more on the Best Time of Year for a Perc Test.