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Subsurface Fact Sheet

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The most common method of treatment and disposal in rural and suburban areas is through the use of subsurface on-site wastewater systems, more commonly called on-site septic systems. Their popularity is due to their simplicity and construction cost. On-site septic systems have two major components: (a) the septic tank, where solids settle and decompose, and (b) the subsurface absorption field, where liquid discharged from the tank is treated by bacteria living in the soil.

illustration of a conventional subsurface system

The DO's and DON'Ts of Conventional Systems:

DON'T use septic tank additives.

DO have your septic tank pumped out every three to five years or as needed.

DON'T flush material such as hair, diapers, cigarette butts or feminine hygiene products because they will not easily decompose.

DO divert roof drains and surface water from driveways and hillsides away from your system.

DON'T drive over the septic tank or drainfield (lateral lines).

DO learn the location of your septic tank and drainfield (lateral lines).

DON'T plant anything over or near the lateral lines except grass because the roots of trees and shrubs can clog and damage the lateral lines.

DO cover the absorption field with grass to prevent erosion and remove excess water.

DON'T do all of the laundry on the same day of the week; spread it out over a weeks time.

DO conserve water to avoid overloading your system.


Signs of Conventional System Malfunction:

  • Pools of water or soggy spots on your lawn near your system

  • Foul odors at soggy areas

  • Sewage backs up into the house

  • Sluggish drains

Water DropOn-site treatment systems are designed to treat and disperse a set number of gallons of wastewater a day. If the amount of wastewater is exceeded, then your on-site system may malfunction. It is recommended that water-conserving fixtures be installed in residences. Please contact your local DEQ office for additional information concerning maintenance of your on-site system.