Many septic experts will recommend frequent septic tank pumping as a solution for failed or failing septic systems.  While this may offer temporary relief, it is in no way a long term solution.  To understand why, let’s look at why a septic tank remains full and is not able to pass water to the drainfield.

The septic tank is positioned between the house and the drainfield.  It’s primary function is to act as a holding tank, allowing bacteria to break down organic solids into simpler forms and gas and solids to settle at the bottom of the tank.  It is important to note that aerobic septic tanks perform the organic breakdown faster and more completely than anaerobic septic tanks.  Incoming sewage displaces “treated” water which travels into the drainfield and is absorbed into the ground.

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Diagram of a functional septic system

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Start of biomat growth in anaerobic septic system drainfield

The anaerobic septic tank has a serious design flaw: the outflowing water from the septic tank contains a high concentration of organic solids and anaerobic bacteria. This solution flows into the drainfield where the water is absorbed into the ground but the solids and bacteria collect at the edge of the gravel bed of the drainfield.

Over time, the organic matter and anaerobic bacteria form a biomat, which grows along the edges and walls of the drainfield.

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Biomat sealing anaerobic septic system drainfield

As it begins to seal the drainfield, water collects in the drainfield because it is the rate of absorption is less than the amount of incoming water.

Eventually, no water can leave the drainfield because it is sealed. As a result, no water can leave the septic tank and it is always full.

Frequent septic tank pumping only creates storage capacity for the system within the tank; nothing has been done to unseal the drainfield and reclaim its storage capacity.

Additionally, frequent septic tank pumping removes the bacteria from the septic tank, eliminating any organic waste processing from occurring (regardless if the system is aerobic or anaerobic). More solids will actually be passed into an already clogged drainfield!

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Biomat sealed anaerobic septic drainfield ponding

Until the biomat is removed and the drainfield can pass water, the system is not functional. This failure mode does not exist, however, with an aerobic septic system.  Aerobic septic systems remove the necessary elements that sustain biomat growth in the drainfield.  Fortunately, anaerobic septic systems can be converted to aerobic systems, restoring functionality and saving homeowners thousands of dollars.