How A Septic System Works
Septic systems are designed to hold, treat, and dispose of household waste water. The liquid portion of what goes into the system will leave the system and may eventually reach groundwater or surface water. Household waste water contains bacteria, viruses, household chemicals, and excess nutrients such as nitrates, all of which can cause health problems. Therefore, household waste water must have adequate treatment to prevent water contamination.
Your septic system has two major parts: a septic tank and a soil absorption system. Waste water from toilets, sinks, showers, and other drains, flows from the household sewer drain to an underground septic tank. There, waste components separate–the heavy solids settle on the bottom, forming a sludge layer, while grease and fatty solids float to the top, forming a scum layer. Bacteria in the tank partially decompose the solids.
Solids will build up in the tank and must be removed periodically by a professional contractor. The relatively clear layer of waste water in the middle is called effluent. Effluent flows from the septic tank outlet to the soil absorption system where most of the treatment process occurs.
The Absorption System
The soil absorption system, also known as the drain field, leach field, or disposal field, consists of gravel-filled trenches containing plastic chambers or perforated plastic pipe. This underground portion of the system accepts effluent from the septic tank outlet. Effluent moves through the pipes and seeps into surrounding soil for final treatment. Soil particles filter out small suspended solids and organic matter, while soil bacteria break down harmful microorganisms and other organic components. Viruses adhere to clay particles in the soil and eventually die. The now treated effluent continues its downward flow through the soil layers.
Managing Your System
As long as your septic system has been properly designed and installed, there are some things you can do to keep it functioning well.
- protect the system from being overloaded with water
- improve the quality of your waste water
- protect the soil absorption (drain field) portion of the system
Less water entering the system means better treatment and longer system life. Keep in mind that as water enters the septic tank, an equal amount is displaced and released into the drain field. When excess waste water enters the septic tank, settling time is reduced, enabling some solids to enter the drain field area. Excess solids in the drain field can cause the system to fail by clogging the soil pores. Clean water from heavy rains or too much lawn watering can also negatively affect the drain field area. Because it is designed to treat waste water, any excess clean water that enters the drain field makes the system work more than is necessary.
You can improve the quality of your waste water by reducing the amount of suspended solids that go into the system. Suspended solids include grease and fat particles and ground-up foods from the garbage disposal. These small particles don’t settle out well in the tank and can end up in the drain field reducing its useful life-span.
Since the drain field area is where most of the treatment occurs, it’s very important to protect this portion of the system. Soil compaction is a major hazard to the operation of the drain field because compacted soil cannot treat waste water. Once compacted, soil can’t be restored; the installation of a costly new drain field is the usual solution to the problem. Examples of things that can cause soil to become compacted include vehicle traffic, heavy objects, and buildings.
A properly designed, installed, and maintained septic system should protect the environment and give your household many years of good service.