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There are two main parts to the basic
septic system: the septic tank and the drainfield.
The Septic Tank
Household wastewater first flows
into the septic tank where it should stay for at least a day. In the
tank, heavy solids in the wastewater settle to the bottom forming a
layer of sludge, and grease and light solids float to the top forming
a layer of scum (refer to the graphic on this page). The sludge and
scum remain in the tank where naturally occurring bacteria work to
break them down. The bacteria cannot completely break down all of the
sludge and scum, however, and this is why septic tanks need to be
pumped periodically. The separated wastewater in the middle layer of
the tank is pushed out into the drainfield as more wastewater enters
the septic tank from the house. If too much water is flushed into the
septic tank in a short period of time, the wastewater flows out of the
tank before it has had time to separate. This can happen on days when
water use is unusually high (laundry day, for example), or more often
if the septic tank is too small for the needs of the household.
The Drainfield
When wastewater leaves a septic tank too
soon, solids can be carried with it to the drainfield. Drainfields
provide additional treatment for the wastewater by allowing it to
trickle from a series of perforated pipes, through a layer of gravel,
and down through the soil. The soil acts as a natural filter and
contains organisms that help treat the waste. Solids damage the
drainfield by clogging the small holes in the drainfield pipes and the
surrounding gravel, and excess water strains the system unnecessarily.
Septic system maintenance is often compared to automobile maintenance
because only a little effort on a regular basis can save a lot of
money and significantly prolong the life of the system. Sound septic
system operation and maintenance practices include conserving water,
being careful that nothing harmful is disposed of through the system,
and having the system inspected annually and pumped regularly. By
educating everyone in your household about what is and what isn't good
for septic systems, they can begin to develop good maintenance habits.
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