Causes of Septic Problems: Misc.
1. The system could be too small for the household. This could be due to greater flow rates than the design allows for, or the system may pre-date the code. The code gives us minimum sizes, with the expectation of 75 gallons per day per person, two persons per bedroom, as mentioned previously. It's possible to exceed the design flow rate (if enough relatives move in!).
2. The system could be too small if the perc test was inaccurate. The slower the soils drain water, the larger the soakdown area needs to be, so the code requires more square feet of "effective leaching area" if the perc. rate is slow. If the system design is based on too quick/fast a perc. rate, the system may be too small for that size house in those soils. The new proprietary systems, where the State has granted very high square feet per linear foot allowances (resulting in more compact systems), are exceptionally sensitive to a perc. result that makes the system smaller than it should be.
3. A tipped distribution box or other distribution flaws can cause part of the leaching area to be overused while the other part is underused.
4. Also, groundwater may be saturating the system if it is constructed below the seasonal high water table.
Mottling is a rust-red discoloration of the soil that can be seen in a test hole. It is used as an indicator that water travels along that layer of soil at least one month out of the year. The layer of soil below it has restricted the water from soaking down any deeper, so mottling indicates a "restrictive layer". Connecticut code requires the bottom of the leaching area to be "eighteen inches above maximum groundwater level". In the absence of water observed in a test hole at a higher level, the restrictive layer indicated by the mottling is the "maximum groundwater level".
The 18 inch requirement prevents groundwater from entering the system directly or by capillary action, and ensures the effluent will be purified within unsaturated soil before mixing with the groundwater. This way aerobic bacteria can do their thing within the soil.
There are two methods for dealing with high groundwater levels: curtain drains, and elevating the system with "select fill". These have been discussed on preceding pages.
5. A broken or collapsed pipe may prevent effluent from reaching all or part of the system. In recent years all pipes distributing the effluent to the leaching components are required to be stronger than before. (ASTM D 3034, SDR 35)
6. Clogging of pipes feeding the leaching system is often due to root infiltration. Again, this is more common in older systems, not only because the joints in older pipes are far more susceptible to roots getting in, but also simply because more time has passed for trees to grow.
7. Improper grading:
The State code is self-explanatory on this topic, and bear in mind that newer systems are often shallow by design, making grading even more important:
"The ground surface over the entire subsurface sewage disposal system shall be graded and maintained to lead surface water away from the area."