Septic Problems - Failed or Plugged Drainfield

Plugged Drainfield - How did this happen?

A plugged drain field can be one of the most costly repairs for your septic system.  Understanding how a drain field may become plugged will help you to prevent it from becoming plugged in the future.  Also see the Don't List.   This will also help you to better evaluate the many technologies that claim to fix failing drain fields.  Drain fields can become plugged by any one or some combination of the following:

Fats oils & grease ("FOG"). FOG that that escapes the septic tank will flow into the drain field and can quickly plug the soil below the drain field. ...more

Silt & Clay particles.  Smaller particles like clay and silt don‘t settle well and are not captured by the septic tank.  These small particles can plug the soil under the drain field. ...more

Garbage disposal. A garbage disposal chops food waste into small particles.  These small particles are not easily removed by the septic tank and can plug the drain field. See also Fats, Oils & Grease.

Water Conditioners/Softeners or any other water supply treatment system may have a backwash system.  The pollutants and minerals removed by these systems will not settle out in the septic tank. If the backwash system is connected to your septic drain, it can plug the drain field.

Paint in any amount that goes down your drain can pass through your septic tank and plug part of your drain field. Washing paint off a brush in your sink is causing damage.

Poisons can kill the organisms living in your drain field and the dead organisms may then plug the soil. Some common poisons include antifreeze, paint thinner, strong acids or alkalis, toxic cleaners, disinfectants, etc.

High flow can wash solids (or fats oil, & grease) out of the septic tank and plug the leaching facility. High flow can also drown the organism living in your drain field and the dead organisms may then plug the soil.  ...more

High groundwater may also drown the organisms in the drain field.   High groundwater may also surcharge the septic tank.  A surcharged septic tank will allow fats, oils and grease to flow over the outlet baffle and plug the drain field. A properly designed system has the drain field located well above the high water table.    However, conditions could change that result in raising the groundwater table.   Local land development or a nearby beaver dam could raise the groundwater in your yard.

Poor Drainage due to stormwater runoff from nearby impervious structures (barn roof, driveway, parking lot, etc.) can flood the drain field.  Even though the flooding may be temporary, it can result in a clogged drain field.  Take a look at the area where your drain field is located.  Are there any drains or other facilities that may be dischargng stormwater onto your drain field?  If so, look for a way to guide the stormwater runoff away from the drain field.  For example you may want to put a gutter on the barn roof or a curb along a paved parking area to direct the runoff away from the drain field.

Roots from nearby trees and other deep-rooted plants can plug a leaching facility.  In most cases, shallow-rooted grass, mowed regularly, is the recommended surface over drain fields.

Impervious covers (driveways, swimming pools, etc.)   Any impervious cover that blocks air flow into the soil will increase the chance that the organisms living in the drain field may die and plug the soil.