What are septic trenches?

If your property has no council sewer main and was constructed approx. 10yrs ago or more than your property most likely has a septic tank which requires septic trenches also known as evapotranspiration beds. Modern systems use a different tank called a HSTP which uses aeration and bacteria to break down solids, then the effluent is pumped out to surface or sub-surface irrigation.

Septic trenches are an important but often overlooked piece of your septic tank systems operation.

The absorption trench is where the treated effluent from your septic system is disposed of once solid material has been separated inside your tank.

How do septic trenches work?

Effluent flows from your septic tank to distribution box which then evenly distributes the effluent to absorption trench/trenches area usually by means of a gravity feed. A combination of friendly bacteria in the soil, plant root interaction and sunshine, the effluent is broken down and made safe before being put back into the environment.

If your septic tank system is overdue for a clean, untreated waste can flow into your absorption trench and limit its ability to effectively dispose of the effluent from your tank.

The solid material that should be contained in your septic tank can flow into your drain field where it blocks the holes that normally allow effluent to pass into the soil of your absorption trench for clean, efficient, and safe disposal.


How do I know if my septic trenches have failed?

There are a view key things to look out for. They can include wet and soggy ground above your absorption trench or unpleasant smells from around your trench field area. Your distribution box holding liquid and not draining. Your absorption trench and the surrounding area should be dry and have no unsightly odours.

Your absorption trench is designed to let the liquid effluent pass through the trench into the surrounding soil through small holes in the pipes that make up your drain field system. The solid material that overflows into your drain field (absorption trench) when your septic tank is too full and needs servicing acts to clog the holes and prevents the effluent from correctly dissipating.

This will eventually destroy the effectiveness of your absorption trench and require complete replacement. A costly exercise.

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