3 Root Causes Of Drain Field Failure

28 September 2021
 Categories: , Blog


A failed drainfield compromises your entire septic system. If effluent can't drain and percolate through the soil properly, then the effluent isn't completely treated before it leaches back into the groundwater. The result is tainted groundwater and standing sewage on the drainfield. Fortunately, it is often possible to restore a drainfield, particularly if you catch problems early. Knowing the causes of a failure can help mitigate extensive damages.

1. Flooding

Flooding can occur due to tank issues or external flooding. An overloaded septic tank, such as one that hasn't been pumped regularly, can begin spilling unprocessed effluent and solids into the drainfield. This flood of solid material can clog drainfield lines and the soil, leading to more percolation and surface flooding. Pumping the tank and cleaning out the drainfield lines may restore the field.

External flooding is caused by rain, snowmelt, or improper irrigation runoff. The field becomes over-saturated to the point that effluent can no longer percolate through it. Restoration may involve draining the field, as well as installing drains and culvert systems that route water away from or around the drainfield. 

2. Biological Stress

Biological stresses are most often caused by the out-of-control growth of the biomat. A biomat is a collection of bacteria and other helpful micro-organisms that help break down the effluent in both the septic tank and in the drainfield. Generally, a biomat is a beneficial part of the septic system, but in some cases, it can grow out of control and begin to block the drain lines that feed into the field.

Restoration is more complicated for biological stress. Often, it is a sign that the field is too small for the system, so expanding the drainfield may be necessary. It may also be possible to clean the drain lines to help clear any clogs caused by biomat growth. At worst, it may be necessary to completely remove and rebuild the existing drainfield. 

3. Compaction

Compaction from tree roots is possibly the most common form. Trees and shrubs can begin to grow over the drainfield or they may encroach from the perimeter. The roots infiltrate the soil and create a dense mat that water can't percolate through. Compaction can also occur from mechanical means, such as driving or parking on the field.

The best solution is prevention, so pull out possible problem plants and don't drive on the field. If compaction damage is already present, then the field may need to be rebuilt so that the soil is once again arable and drains well.

Contact a local drainfield restoration service to learn more.