What causes drain field failure?

Drain-field problems can have several causes. Understanding the possibilities can help a property owner describe useful observations.

Biomat formation

A biomat is a layer of organic material that builds up along the soil interface in drain-field trenches. It can restrict percolation when the tank is overfull, solids reach the field, or the field receives more hydraulic load than the site can absorb.

Pumping and system loading

A maintenance interval that does not fit the tank, household, or system can allow solids to reach the field. Water-use patterns, records, and county guidance should be reviewed with General Septic rather than relying on a universal schedule.

Root intrusion

Tree and shrub roots can enter lateral pipes, crack pipes, or block lines. General Septic or a designer can explain how vegetation and site conditions should be considered.

Physical damage

Heavy vehicles or equipment over a drain field can compact soil and damage lateral pipes. Keep vehicles away from the field area.

Seasonal high water tables

In western Washington, wetter seasons can temporarily saturate low-lying or shallow-soil drain fields. Describe recurring seasonal observations to General Septic or the applicable health authority.