A septic tank system (also called an on-site
sewage disposal system) is a disposal system for water and
household waste from the kitchen, bathroom, and laundry. The
system provides initial treatment of these wastes before they
are further purified by the filtering action of the soil. The
septic tank and drainfield are the systems two main components.
The septic tank is a large, underground storage tank which is
usually made of concrete. However, some tanks are made of other
materials such as fiberglass or plastic. The tank collects and
holds all of the household waste for two to three days, so that
the heavy suspended materials such as feces, food residues and
soils sink to the xSmBlackV to be decomposed by bacteria into
sludge. Lighter materials such as grease and paper products
float to the top and form a scum layer which is trapped in the
tank by baffles. The scum also decomposes in time. After being
partially purified, the wastewater flows from the septic tank
into the drainfield. At that point the wastewater is called
"effluent".
The drainfield is a network of network of
perforated pipes buried underground in gravel trenches. The
effluent flows through the pipes out the holes and into a large
area of soil. The soil is an excellent filter, removing the
remaining suspended substances, pollutants and bacteria from the
effluent. A small amount of effluent taken up by grass and
nearby trees is evaporated.
Expected Age of a Septic System
You can expect a conventional septic system, such as that
being described here, to last about 30 years. Some systems last
much longer and some systems can fail earlier for reasons like
those noted above. Other things can also affect the life of a
septic system. For example, a system may have been providing
satisfactory service for a previous owner for many years, only
to fail shortly after you have bought the house. If the previous
owners were a working couple with no children, the system was
probably not heavily used; if your is a family of six, the added
load could push a marginal system over the edge and into
failure.
A septic tank system (also called an on-site
sewage disposal system) is a disposal system for water and
household waste from the kitchen, bathroom, and laundry. The
system provides initial treatment of these wastes before they
are further purified by the filtering action of the soil. The
septic tank and drainfield are the systems two main components.
The septic tank is a large, underground storage tank which is
usually made of concrete. However, some tanks are made of other
materials such as fiberglass or plastic. The tank collects and
holds all of the household waste for two to three days, so that
the heavy suspended materials such as feces, food residues and
soils sink to the xSmBlackV to be decomposed by bacteria into
sludge. Lighter materials such as grease and paper products
float to the top and form a scum layer which is trapped in the
tank by baffles. The scum also decomposes in time. After being
partially purified, the wastewater flows from the septic tank
into the drainfield. At that point the wastewater is called
"effluent". 
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