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Maintain Your Septic System for a Healthy Illinois River

This is an illustration that demonstrates how septic tanks hook up to a house.








Private on-site wastewater treatment systems – “septic systems” - account for a large proportion of wastewater treatment in the Illinois River Basin. They are used by virtually all rural homes and many in small towns.


In Oklahoma, the Department of Environmental Quality (DEQ) regulates treatment of sewage to protect health and prevent pollution. This includes both municipal treatment plants and on-site systems. However, in practice, rural homeowners are responsible for assuring that their own septic systems are maintained properly.

Wastewater treatment is necessary to prevent the spread of disease and to keep pollutants out of water resources. They control:


  • Pathogens (bacteria, viruses, parasites, etc.) that make water unsafe.
  • Nutrients (phosphorus and nitrogen) that stimulate algae and other plant growth, leading to degraded habitat and fish kills.
  • Other pollutants, including toxics, oxygen- consuming organic matter, detergents and hazardous household chemicals.

 This diagram shows a septic tank-drained treatment system.

Figure 1. Diagram of septic tank-drained often if there is a garbage disposal.
treatment system.





Septic systems that are not installed and maintained properly release all these pollutants to our waterways and groundwater.


Types of Septic Systems

Most rural homes have conventional septic tank/soil absorption systems. These systems use gravity to collect wastewater in a tank and distribute it to a subsoil absorption field (drainfield) for further treatment (Fig.1).

Conventional septic systems are recommended for most sites because they are the least expensive and most easily maintained. However, there are alternative systems better suited to unfavorable sites, such as very shallow soils (over bedrock), heavy clay soils, or in soils with a high water table.


How the Conventional Septic System Works

A conventional septic system has two main components.


  • Septic tank (Fig.2): Separates the solids to prevent them from entering the soil absorption field. Heavy solids settle out to a sludge layer at the bottom. Lighter solids, fats and oils form a floating scum layer. Some pollutants in the wastewater are digested by bacteria, converting them to a gas that escapes or to a liquid that is passed to the absorption field.
  • Absorption field: A pipe carries the liquid effluent from the tank to a distribution system consisting of a distribution box and laterals. The laterals distribute effluent to the soil, where liquid and remaining solids are stabilized by soil microorganisms, and pathogens are destroyed.

 This illustration demonstrates how a septic tank works.


Figure 2. Septic tank chamber separates
solids from liquids. (Courtesy Watershed Committee
of the Ozarks)




Excess solids entering the drainfield can interfere with its function, clogging the system and causing sewage to back up. Regular pumping of the tank is essential every 2-4 years for average families, more often if there is a garbage disposal.


Septic System Tips

Install it right!


  • Use only a certified septic system installer. Call DEQ for assistance.
  • Install a larger tank or pump more frequently if you plan to use a garbage disposal.
  • Install septic system at least 75 feet away from a well or spring; 100 feet if the well is down slope.
  • Do not install pavement, trees, or buildings on top of the absorption field.
  • Keep a map showing where your tank, distribution boxes, and lateral lines are. This is easiest during installation.
  • Divert water from downspouts and foundation drains away from your absorption field. Excess water can overload your system.


Maintain it for long life and clean water!


  • Never allow vehicles to drive over the septic tank or the absorption field.
  • Have your septic tank pumped by a licensed pumper every 2 to 4 years, until you learn how fast sludge and scum layers build up.
  • Use water saving devices. Reducing water flow extends system life and reduces pollution.
  • Do not use any septic tank additives. They do not eliminate the need for periodic pumping and may shorten the life of your absorption field.
  • Never dispose of solids, diapers, pesticides, solvents or toxic materials in your septic system. Toilet paper and normal household cleaners are OK.


Where To Go For Help

  • Oklahoma Department of Environmental Quality (DEQ) licenses installers and inspects and approves new installations. Call 1-800-522-0206 for information and the location of your local office.
  • County Conservation District have information on programs to assist in system replacement.
  • County OSU Cooperative Extension Service has publications and information on conventional and alternative septic system
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