Encyclopedia & FAQ's

DIY Frequently Asked Questions / Septic Tank


  • DIY Frequently Asked Questions / Septic Tank')"> A large watertight settling tank that holds sewage while it decomposes by bacterial action.
  • Made of asphalt coated steel, redwood, concrete, concrete block, clay tile or brick.
  • Tanks must be sized to suit the house. Twobedroom homes need minimum 750gallon tanks, according to the U.S. Public Health Service. Threebedroom homes need 900gallon tanks and fourbedroom homes require 1,000gallon tanks. Garbage disposers, washing machines and dishwashers are figured in this estimate.
  • Household sewage flows into the septic tank anddecomposes. Sludge collects on the bottom of the tank and liquid effluent flows out to a distribution system. The distribution system is a series of underground disposal lines that radiate outward from a central distribution point; the effluent seeps into the earth.
  • Sludge remaining in the tank must be cleaned out periodically to prevent this layer from building up enough to cause clogging of disposal lines or household sewer lines.
  • Under ordinary use, the tank may need cleaning at two to four-year intervals, but most experts recommend that the sludge level be inspected every 12 to 18 months. Inspect by opening a special manhole cover or trapdoor located at or near ground level.
  • Septic tank cleaners dissolve sludge through enzyme activators that regenerate the natural bacterial activity of decomposition for which the tanks were designed. These natural bacterial activators continue from the tank into the drain and tile field.