Treatment Options for a Drain Field Biomat

When a thick, dark growth covers your drain field, this substance is called a biomat and it is not a good sign. Biomats occur when the drain field is not filtering effluent from the septic tank properly, resulting in an organic growth above ground. If your drain field is forming a biomat, this is a warning that your septic system needs service. Treating and servicing your septic system quickly can eliminate a biomat and may prevent a septic failure.

Schedule an Inspection and Service

First, call your local septic professional and schedule an inspection and service. If left unchecked, a biomat can destroy your septic system, requiring a new tank and drain field be installed. A maintenance service of tank pumping and inspecting your system may identify issues that can help treat your biomat.

Change Your Habits

It may not be a problem with your septic system that is causing your biomat; it may be how you are using your septic. Using excessive water, putting chemicals down the drain, using anti-bacterial soaps/cleansers and anti-biotic medications can all impact your septic system’s ability to breakdown solid waste. This can cause solid particles to flow out to your drain field, feeding the biomat that is growing and suffocating your system. Cut down on water use and be careful not to put items down the drain that can kill the good bacteria in your septic tank.

At the first signs of a biomat formation on your drain field, call your local septic service company and begin evaluating your septic use. Quick action on your part could save your septic system and save you thousands of dollars in replacement costs.

Posted on behalf of:
Metro Septic LLC
1210 N Tennessee St
Cartersville, GA 30120
(678) 873-7934


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.