Proper Care & Maintenance of Private Sewage Treatment Systems

Over 30% of the housing units in Kankakee County rely on individual on-site sewage treatment facilities for disposal of domestic waste water. When properly installed, operated and maintained, on-site systems can provide homeowners with many years of trouble free service. If neglected, these systems may fail, leading to potential public health hazards for the homeowner. Regular maintenance is essential to ensure loong life of a septic system.

This brochure describes the proper operation and maintenance of individual on-site septic systems. This information will facilitate mainenance and help prevent septic system failures.

Private Sewage Treatment Systems

Today’s private sewage treatment system contains three components: the house where the waste is generated, the septic tank where the partial treatment takes place, and the subserface seepage system, which provides for final treatment. Wastewater generated within the house comes from a variety of sources including showers, toilets, sinks, garbage disposals, dishwashers, bathtubs, jacuzzi/whirlpools, floor drains and washing machines. Most of the solid waste comes from the kitchen sink, garbage disposal and toilets. Other facilities produce quantities of wastewater with only limited amounts of soil and detergents. The total volume of wastewater is about 50 gallons per person per day. To ensure sufficient performance of the system throughout its lifetime, an estimated wastewater flow of 200 gallons per bedroom per day is required for single family dwellings.

The Septic Tank

The wastewater leaving the house is collected and temporarily stored in the septic tank. The septic tank is a large container, usually constructed of plastic or concrete. Heavy solid particles in the wastewater will settle to the bottom of the tank creating a thick sludge layer. Grease and other light material will accumulate in a floatng scum layer. Floating material is retained in the tank by vertical baffles. The septic tank retains the wastewater for approximately 24 hours, allowing the solids to separate and settle out. This permits bacteria to partially decompose and liquify the solids, resulting in a reduction of suspended solids and nitrogen.

The volume of sludge and scum gradually increases and must be pumped out periodically to ensure that solids will not block the septic tank or overflow into the subsurface seepage system. Clogging the field with solids can result in premature failure of the absorption field and may require costly repairs or replacement. Pumping will not affect the biological activity in the tank. All the necessary bacteria occur naturally in the incoming sewage. Pumping should be done at least once every two years depending on the amount of water usage.

The inside of the septic tank is accessible through openings in the tank lid over the inlet and outlet baffles. A center opening in the tank lid also allows access for pumping. The locations of these openings vary with the size and brand of septic tank. All landscaping should be done in a manner that allows proper access for tank inspection and pumping.

The Subsurface Seepage Field

Partially treated liquid waste flows from the septic tank to the subsurface seepage system where it is absorbed into the soil. Various subsurface seepage system designs are available, such as seepage trenches and seepage beds. Seepage systems are installed at specific distances above water table and bedrock formations. Subsurface seepage systems should not be constructed in areas where the ground water table is within two feet of the bottom of the trench or the bed. Subsurface seepage systems should also provide at least four feet of separation between the seepage trench bottom and local bedrock formations below the system. This will help protect ground water supplies from contamination.

The size of an absorption area is based on the volume of wastewater generated in the home and the permeability of the soil. Permeability, the ability of water to flow through the soil, is determined through percolation tests or is estimated from county soil survey information. The number of bedrooms in the dwelling and the percolation test results determine the absorption area.

In areas where a conventional septic tank/soil absorption system is unsuitable (such as areas with high water tables or slowly permeable soils), it may be possible to modify site conditions or use alternative systems.

In areas with high water tables, for example, underdrains or curtain drains may be used to lower the water table. Another option is to raise the level of the soil surface with layers of fill soil.

When it is not practical to modify the site, consider an alternative system. For example, the mound system and the aerobic system are alternatives that may be used in areas with high water tables or slowly permeable soils.

The aeration system consists of a chamber that mechanically aerates (mixes air with) the effluent and decomposes the solids. Effluent is discharged to an absorption field or, after chlorination, to surface water or an evaporation pond.

Other alternatives include sand filters, lagoons, electro-osmosis systems, dropbox distribution systems, serial distribution systems, pressure-dosed distribution systems, and leaching chambers. In general, alternative systems are more costly to install and operate than conventional septic tank/soil absorption systems and may require additonal maintenance.

For more information on alternative systems, contact your local Health Department [information at top].

Water Use Do’s and Don’ts

The use of water in the home is critical to the life of the septic system. Water should not run continuously during the washing and rinsing of dishes. Repair leaky faucets and toilets immediately. Down spouts and other clear water discharges should not be directed into the septic tank. It is important to remember that all water drained into the septic system must be absorbed into the ground. Non-biodegradable items should not be flushed into the septic tank. Coffee grounds, cigarette butts, paper towels, disposable diapers and similar solid objects will not decompose readily in the septic tank. Disposal of such objects into the septic tank may result in a blockage of drain lines or other system failure.

Small amounts of detergent, bleach and household cleaners will not harm the septic system. However, care should be taken not to flush large quantities of these materials into the septic systems. Homeowners should not allow lye or caustics to drain into septic systems. Materials of this type may destroy the bacterial action in the septic tank and disrupt the proper treatment of wastes.

In summary, the following points should be carefully observed by individuals using septic systems for sewage treatment.

  • It is recommended not to install a garbage disposal or grinder. They markedly increase the load of suspended solids in wastewater, causing more rapid buildup of sludge in the septic tank and resulting in a premature failure of the system. If a grinder must be installed, the size of the septic tank must be increased 1½ to 2 times the normal tank volume. The tank will then be better able to handle the increased level of solids.
  • Reduce water usage. Do not run water continuously while rinsing dishes or thawing frozen food products. Consider installing low-volume or pressure assisted toilets, or limiting flushes of older five-gallon tank toilets. Try to stagger the use of the washing machine (i.e., do not run six loads Monday and none on the other days).
  • Divert all clear water discharges away from the septic system. This includes footing drains, sump pumps, gutters, downspouts and water softeners.
  • Avoid flushing non-biodegradable items into the septic system.
  • Avoid the placement of patios, driveways, swimming pools or garages over the septic system.
  • Pump the septic tank at least once every two years and inspect the baffles in the septic tank after each cleaning.

Do Not Dispose in the Septic System

  • fats
  • grease/cooking oils
  • disposable diapers
  • auto fluids (oils, etc.)
  • household cleaning fluids
  • lye or caustics
  • paper towels
  • cigarette butts
  • antifreeze
  • gasoline
  • coffee grounds

Trees and Septics

Tree root invasion of septic tanks, absorption fields, and drop boxes, is a long standing problem in the maintenance of on-site treatment systems. Many trees and shrubs readily invade these systems because they can provide air space, water and nutrients. Not all trees and shrubs invade septic systems. Listed here are a number of species and the likelihood of their roots invading septic systems. The list* is not exhaustive but includes those plants for which there is reliable information.

Trees with Roots Commonly Invading Septic Systems

  • Boxelder
  • Red Maple
  • Silver Maple
  • Red Cedar
  • Cottonwood
  • Weeping Willow
  • Peachleaf Willow
  • Corkscrew Willow
  • Black Willow
  • American Elm
  • Siberian Elm
  • Slippery Elm

Trees With Roots Rarely Invading Septic Systems

  • Norway Maple
  • Sugar Maple
  • White Ash
  • Green Ash
  • Red Pine
  • White Pine
  • White Oak
  • Bur Oak
  • Red Oak

Shrubs With Roots Commonly Invading Septic Systems

  • Gray Dogwood
  • Autumn Olive
  • Pussy Willow
  • Common Buckthorn
  • Red-osier Dogwood
  • Sandbar Willow
  • Forsythia

*Information furnished by Morton Arboretum

For further information or additional [paper] copies of this pamphlet, contact the:

Kankakee County Health Department
2390 W Station St
Kankakee, Illinois 60901
(815) 937-7860 (voice)
(815) 037-8520 (TDD/TTY)