Image Source: Produced by Agricultural Communications, The Texas A&M University System, EPA
A septic system is a highly efficient, self-contained, underground waste water treatment system. Because septic systems treat and dispose of household waste water onsite, they are often more economical than centralized sewer systems in rural areas where lot sizes are larger and houses are spaced widely apart. Septic systems are also simple in design, which make them generally less expensive to install and maintain. And by using natural processes to treat the waste water onsite, usually in a homeowners backyard, septic systems don’t require the installation of miles of sewer lines, making them less disruptive to the environment.
If you are like most homeowners, you probably never give much thought to what happens when waste goes down your drain. But if you rely on a septic system to treat and dispose of your household waste water, what you don’t know can hurt you. Proper operation and maintenance of your septic system can have a significant impact on how well it works and how long it lasts.
A septic system consists of two main parts-a septic tank and a drain field. The septic tank is a watertight box, usually made of concrete or fiberglass, with an inlet and outlet pipe. Waste water flows from the home to the septic tank through the sewer pipe. The septic tank treats the waste water naturally by holding it in the tank long enough for solids and liquids to separate. The waste water forms three layers inside the tank. Solids lighter than water (such as greases and oils) float to the top forming a layer of scum. Solids heavier than water settle at the bottom of the tank forming a layer of sludge. This leaves a middle layer of partially clarified waste water.
The layers of sludge and scum remain in the septic tank where bacteria found naturally in the waste water work to break the solids down. The sludge and scum that cannot be broken down are retained in the tank until the tank is pumped. The layer of clarified liquid flows from the septic tank to the drain field or to a distribution device, which helps to uniformly distribute the waste water in the drain field. A standard drain field (also known as a leach field, disposal field, or a soil absorption system) is a series of trenches or a bed lined with gravel or course sand and buried one to three feet below the ground surface. Perforated pipes or drain tiles run through the trenches to distribute the waste water. The drain field treats the waste water by allowing it to slowly trickle from the pipes out into the gravel and down through the soil. The gravel and soil act as biological filters.