Signs of Septic Drain Field Failure

The drain field is the last stage of your system. Effluent leaves the tank, passes through the D-box and soaks into the soil through the field lines. When the soil stops absorbing, the whole system backs up.

Concrete septic distribution box exposed in an excavation, with outlet pipes running to the field lines — The distribution box sends equal flow to each trench of the drain field. If it tilts or cracks, one trench takes the load and fails first.

What you may see outside

Grass over the field that is greener, thicker or wetter than the rest of the yard
Soft, spongy or standing water over the field
A sewage smell in the yard
Effluent surfacing at the field or downhill from it

What you may notice inside

Slow drains throughout the house
Gurgling in pipes
Backups in the lowest fixtures, often after laundry

It is not always the field

Drain field lines laid on washed gravel in an open excavation, fed from a black distribution box — Drain field lines spread effluent through gravel and soil. When the soil under them stops absorbing, water rises to the surface above the field.

A full tank, a blocked pipe, a failed D-box or a broken pump can all produce the same signs. Checking the tank, the D-box and the pump first is cheaper than assuming the field has failed.

Why fields fail

Overloading with too much water, solids escaping from a neglected tank, compaction from vehicles, roots, and age are the usual causes. Regular pumping and spreading water use through the week all help.

What to do

Cut down water use, keep people and pets off wet areas and have the system traced from the house to the field. Findings can tell you whether repair is possible or whether the field needs replacing.

Related services

Questions about this guide

Will pumping repair a failing drain field?

A pump-out does not restore damaged pipes or solve every drainage problem. Wet ground and odour need assessment of the tank, distribution, field and site conditions before selecting a repair.