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 more traditional septic system drain fields. Most chamber systems are “gravelless” 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 systems last 20-30 years, some cite 15 to 40 years as the “normal” lifespan of a drain field. 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
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