Q: We had a chamber septic system we had installed 15 years ago when we built our house. They hauled 19 truckloads of K4 sand, no gravel (see system design below). We’ve pumped it regularly and now we are selling. We had a septic inspection done only to be blindsided that the system is over-saturated and in need of replacement.
We have come to believe that chamber systems are inherently not a good design. We’ve talked to both the original engineer and our septic installer, and they both talk of retrofitting the existing system, D box replacement, etc. We’ve had no issues at all. It’s a 5 bedroom home and only 3 people have lived here for 4 years. Thoughts on our situation? I could provide you with more details regarding the construction. Any insight is appreciated. – Lori
A: A chamber-type drain field uses engineered plastic chambers to disperse the effluent rather than the perforated plastic pipes placed in gravel trenches used in traditional septic system drain fields. Most chamber systems are “gravel-less” or use just a little gravel below the chamber. The chambers typically sit on native soil and disperse the effluent directly to the soil, rather than through a gravel bed first. Chamber systems work best with well-drained soil with a good perc rate.
However, in your case, it looks like they brought in a large volume of fill below the chambers, presumably to replace the soil that was not suitable for a drain field. That may explain why they chose to use a chamber system on your site.
Chamber systems are often used where gravel is difficult or expensive to obtain or where traditional gravel trenches may not work well. For example, they may be used on steep sites, undersized sites, or sites where the water table or ledge it too close to the surface
Proponents and marketers of chamber systems claim that they are more efficient than traditional gravel drain fields, and that therefore the drain field can be reduced in area. In fact, some jurisdictions allow smaller drain fields with approved chamber systems. However, there is little scientific evidence backing these claims and many installers feel that these systems perform no better, or worse, than traditional systems.
Chamber systems were first introduced in the late 1980s but are still not widely used, mainly because they are more expensive. For the most part, they seem to work as advertised, but independent data comparing chamber systems to conventional gravel trenches is hard to come by.
As for longevity, 15 years is certainly on the short end of the range, but not unheard of. While most septic system drain fields last 20-30 years, some cite 15 to 40 years as the “normal” lifespan. Some alternative systems have special maintenance requirements that can contribute to early failure if not followed closely.
It sounds like you maintained your septic system properly and used it lightly. So that points to problems with the original design. What does the original engineer have to say about your system’s short lifespan? Clearly you don’t want to pay thousands of dollars for another 15-year system.
An excellent report on Gravelless and Chamber Septic Systems was published by the former National Small Flows Clearinghouse, an EPA-funded organization on rural wastewater systems. — Steve Bliss, BuildingAdvisor.com
Read more on Alternative Septic Systems
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
Infiltrator sadness says
infiltrator System Failed in 9 Years
Our low-profile infiltrator system fail after 9 years. Had 2 different companies out to inspect and it appears despite being installed correctly it just got plugged with biomat. We were on a regular pump cycle of 2 years on a 1500 gallon tank. 3 people living in the house. It’s insane that a system would fail after such a short time. The companies are saying there are seeing more failures around this age for the low profile ones. The technology just sucks. Given any option to do pipe and stone – take it. Tried and true.
Adam says
I’m in the exact same situation! 13 years old! trying to do a repair of existing systmem
Septic blows says
Did you find a fix. I’ve had a septic company say they dig a trench at the end the field and then jet the lines to remove all biomat in sand and on chambers. It’s $5k but that may be the fix, of course, no guarantee.
dave says
i just had chamber field done seems to me much better since i have oak trees that plugged up my 5 inch pipes we will see
Chrissy says
Why Did Infiltrator System Fail So Quickly?
Hello Building Advisor,
We just received the shocking news that our 9 year old septic system has failed largely due to the infiltrators that were used. Any information you able to share with regards to infiltrators would be helpful. Thank you in advance.
buildingadvisor says
Sorry to hear about your situation. The average life of a drain field ranges from 20 and 30 years or more. Failure in 9 years indicates serious problems with the design, installation, or use and maintenance of the system. Or there may be multiple causes, as there often are when things go this badly. For example, there may be improper fill material or depth along with a poorly drained soil type or high seasonal water level.
Perhaps the system was overloaded by former owners of the house, or problem materials were put down the drains, leading to clogging of the soil with solids – the ultimate fate of all drain fields. There are many factors that determine the longevity of a drain field, and many possible causes of early failure.
Chamber systems are promoted as a good solution for sites with limited space for a drain field. The manufacturers claim that you can downsize the drain field with chambers as they hold more water than perforated pipe (a design concept accepted by some municipalities). While it’s true that chambers can store more water than traditional perforated pipes, most experts agree that the ultimate performance of the system is the soil area used to process the effluent.
With less soil area, less treatment can take place regardless of the water-holding capacity of the chambers. This is especially true with dense, clayey soils. So an undersized drain field may be part of the problem.
I would recommend having a consultant such as septic system designer, sanitary engineer, or installer evaluate the current system and the cause of failure, so you don’t repeat it in the new system.
Our sister site, Inspectapedia, has a good article on the longevity of chamber-type systems and factors that can lead to early failure. The only data I’ve seen on the topic are studies published by Infiltrator Systems, which manufactures chamber systems. Not surprisingly, their data shows that chamber systems last as long as traditional pipe and gravel trenches and have the same early failure rate of under 2% of systems.
I’ve heard anecdotal stories of chamber systems failing prematurely, but it’s not clear if the chambers were the cause as conventional systems can also fail early.
Bill says
Chamber System Failed Inspection
I just had a septic inspection on a home I’m buying. It has a chamber system from 2004. The inspector showed me video of the chambers as I was there watching him do his work. The 4″ pvc pipes had standing water in them several feet before the actual chamber and all 8 pipes that lead to chambers were this way. Not one chamber was dry, all had standing water up to the 4″ pvc pipes leading into them. He told me the system has failed and the ground is no longer draining the water.
Current homeowner had a second opinion by another inspector who passed the system. From my understanding, standing water in the drain chambers is not a properly functioning system. I’m thinking because we pumped the system when the initial inspection was done, that the chambers had time to filter out the water and now appear functioning properly with the new inspection done only a week later. What are your thoughts?
Chambered systems, from what I’m being told, we’re a cheap alternative way to do a septic in the early 2000s and most companies shy away from them. I don’t feel comfortable buying this home now. Thanks
Chris Adam says
All leach fields perc at different rates. This perc rate can also fluctuate depending on many variables. Examples: Heavy rainfall, over irrigation, heavy household use, disposing of improper liquids into leach field, etc. As long as there isn’t effluent backing up into house, the system is working properly. Although it’s not ideal, the best test is to live in the house and see what happens. I’d work out a purchase price with the cost to improve leach field figured in. But I would not do any work until problems arise. Best of luck.
Lori says
Cost To Repair Failed Chamber System
I wanted to follow up with you since you were so kind to provide insight into our septic situation. We’re going to do a modification to the existing system using pipes and stone. It’s called in NJ an in-kind repair. They’ll take away minimum of 2 ft of K4 sand. My husband knows all the lingo. Engineering costs will run roughly $1200, and installation remains to be seen until plans are drawn. We’re guesstimating $11K. It has been a tough pill to swallow.
Apparently these chamber systems were thought to be much more effective than they have proven otherwise, and have been told we’re lucky it lasted as long as it did. Definitely don’t feel lucky in any capacity. We trusted the engineering firm. However, they’re not the only ones to design these chamber systems.
Regardless we have to make decisions and move forward to complete the sale of our home. Absolutely we will be sure to cross all Ts when caring for a new home should it have a septic system. Perhaps we contributed to this outcome in some way, but we’ll be doing everything to gain knowledge to extend the life of our septic system should our new home have one.
Thanks for your time. It’s appreciated!
Richard Piluk says
Placing chambers directly on sandy fill that is not compacted can result in the chambers sinking into the fill, eliminating the void space in the chambers.
Placing the Chambers on a layer of geogrid will avoid the sinking.
Did the area of the system settle over the years and become a low spot that now collects surface water?
[Editor’s Note: Richard is a public health engineer who specializes in troubleshooting failing septic systems.]
Lori says
Yes it absolutely has settled some and collects some water. However after 15 years, our home is under contract, and we’re about to replace the field bed. What choices would you suggest for remedying it? Would you hold the original installer/engineer accountable in some capacity?
Richard Piluk says
You should be able to salvage the 19 truckloads of K4 sand and reuse your the disposal bed. If the chambers have settled and are now full of sand they will need to be dug out and replaced with a new distribution system. You should find that the sand just inches below the chambers is relatively clean.
Once the chambers are removed and the clean sand is exposed, you will need to work with the local regulators and engineer to resign a new distribution method for the system. If the same distribution system is recommended, chances are the new chambers will not settle again since the sand should now be compacted after 15 years.
I would recommend using far fewer rows of chambers and backfilling them with clean pea gravel instead of sand. The pea gravel will give more structural support to the chambers and eliminate the possibility of sand entering the chambers from the sides. There are ways to improve the infiltration of the wastewater into the sand below but they will need to be reviewed and approved by your local regulators.