Homes that are built far from city sewage lines (this includes all rural homes and many suburban homes) need to depend on a private sewage system to manage waste disposal from the household plumbing system.
Septic tanks allow for a more acceptable method of home sewage disposal. They're made to decompose solids and treat sewage by bacterial action prior to seeping away into the earth. The tank itself is typically built of masonry or steel and it is watertight in structure. As sewage from the house line gets into the tank, solids split up from the liquid and settle to the
bottom. Bacterial action then works to break down this gathered matter. The insoluble part stays on the bottom of the tank, while liquids overspill into a series of disposal lines which are buried below the soil and go outward from a central distribution point in different directions.Known as the drainage field, this network of disposal lines
comprises of large-diameter clay pipe which is laid out so that seepage happens through the joints between each section. The set up of this drainage field and the size of the septic tank needed depend on the number of residents in the house and on local soil conditions.Since septic tanks are made to keep a layer of sludge (decomposed solids) at the bottom, they should be cleaned out now and then to prevent this solid layer from developing enough to cause clogging of the disposal lines. Under average use the tank may need cleaning at 2- to 4-year intervals, but most experts urge that the sludge level be inspected every 12 to 18 months. This is achieved by opening a special manhole cover or trapdoor situated at or near ground level. This inspection, and cleaning when needed, is best achieved by a specially equipped septic tank serviceman.