The Septic Tank

The septic tank is a small, on-site sewage treatment and disposal  system buried in the ground. The modern septic tank is a water-tight box usually made of pre-cast concrete, concrete blocks, metal, or  fiberglass. When household waste material enters this box, several things occur:

• Organic solid material floats to the surface and forms a layer of what is commonly called "scum". Bacteria in the septic tank biologically convert this material to liquid.
• Inorganic or inert solid materials and the by-products of  bacterial digestion sink to the bottom of the tank and form a layer commonly called "sludge".
• Only fairly clear water should exist between the scum and the sludge layers. It is this clear water - and only this clear water - that  should overflow into the soil absorption area.

Solid material overflowing into the soil absorption area should be  avoided at all costs. It is this solids overflow that clogs soil pores and causes septic systems to fail. Two main factors cause solid material  to build up enough to overflow: bacterial deficiency and lack of sludge removal.

Bacteria must be present to digest and liquify the scum. If not digested, the scum will accumulate until it overflows, clogging the soil absorption area.

The sludge in the septic tank - inorganic and inert material and by  products of bacterial digestion - is not biodegradable and will not decompose. If not removed, sludge will accumulate until it overflows,  clogging your leachfield.