Biomat is a layer of biological material that forms in the septic field under and around the sides of the drain field lines. Biomat is an important part of the septic system because it helps treat the waste. However, excessive biomat formation can cause serious problems with a septic system and lead to a costly drain field repair.
In a typical septic system, waste water flows from the home to a septic tank. Once in the tank, the waste water is held for a period of time allowing solids settle to the bottom of the tank. The liquid effluent then flows out into the drain field which consists of a series of perforated drain lines buried a few feet under the ground in trenches filled with gravel and soil.
The perforations in the drain field lines allow the waste water to leach into the soil. Bacteria grows in the gravel and soil around the drain lines. This bacteria and other microorganisms in the soil further treat the effluent by digesting small solids and pathogens .
As the bacteria grows, it forms a slimy layer under and along the sides of the drain field lines called biomat. The biomat slows the rate at which the soil can absorb the effluent, but in a properly designed septic system the drain field is large enough to accept all of the effluent even with a thin layer of biomat.
However, if the biomat grows too thick, the effluent will begin to pool and seep to the surface or back up into the home. Regular septic system maintenance such as pumping and inspection of your septic tank will help maintain the proper level of biomat growth.
