What Is a Septic System?
The septic tank serves as a settling basin where solids accumulate and are gradually broken down by bacterial action.
Some of the solid waste is actually liquefied by this "natural bacterial decomposition," however, the rest of the waste accumulates in the bottom as a layer of sludge. Additionally, a small percentage of this waste (mostly fats and oils) float to the top of the tank to form a layer of semi-solid scum.
How does it work?
Those of us living in more rural areas have been forced to learn about the maintenance and working of the sewage treatment facility attached to our home, "the septic system." Usually a septic tank is connected to a drainage field or seepage pit of some kind. If properly maintained, a well-designed system will last almost indefinitely. However, if it is neglected for an extended period of time, it can back up and clog the drainage field. This neglect can result in an expensive excavation and even a replacement of the drain pipes that could cost thousands of dollars.
Although designs vary, most septic tanks consist of a watertight, below ground tank that should have one or two manhole covers (buried below ground) to provide access for cleaning and inspection. Sewage from the house flows into the tank through an inlet pipe near the top on one side. It flows out through a discharge or overflow pipe at the other side. The pipe may end in a large tee fitting or into a baffle (wall) preventing the effluent from flowing straight across the tank from one pipe to the other. The incoming sewage will be diverted downward with a minimum of splashing, allowing the solids to sink to the bottom. Outgoing effluent is drawn from below the top layer of the floating waste (grease, oil, and scum) so that only liquid waste or solids that have been liquefied by the bacterial action going on at the bottom of the septic tank are discharged out into the drainage field.
Since solids will continue to build up at the bottom of the tank, it is imperative that the septic tank be pumped out periodically. Remember, sludge is not biodegradable; if it's not pumped out, sludge will accumulate until it overflows the tank.
It is important to get the septic tank cleaned before the sludge level gets high enough so that the solid material at the bottom, or the semi-solid scum at the top, can flow out into the drainage field. This will quickly clog the drainage pipes and the soil into which they drain.