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What is a Septic System?
There are a number of different septic systems, each
with its own design. The conventional system is the most
commonly used in Coweta County (figure 1). It consists
of three main parts: the septic tank, drainfield, and
the soil beneath the drainfield.
The septic tank is a watertight concrete box. It is
buried in the ground just outside the home. The tank is
usually precast from reinforced concrete and can be
purchased from concrete manufacturers.
All of the wastewaters from the home should flow into
the septic tank. Even waters from the shower, bathtub,
and washing machine can contain disease-causing germs or
environmental pollutants. As wastewater flows into the
tank, the heavier solid materials settle to the bottom
(forming a sludge layer), the lighter greases and fats
float to the top (forming a scum layer), and the liquid
(sewage effluent) flows out of the tank. An outlet
baffle (or a sanitary tee at the outlet end) prevents
solids from flowing out with the liquids. The tank’s
primary purpose is to retain the solids while releasing
sewage effluent to the drainfield.
The tank temporarily holds household wastes and allows a
small amount of pretreatment to take place (figure 2).
The tank is connected to the drainfield by a buried
pipe. A typical drainfield consists of trenches
excavated into the sub-soil. After the trenches are
covered with soil, the area must be landscaped to keep
surface waters from ponding over the drainfield.
The drainfield has also been called the nitrification
field or the soil absorption field.
The sole purpose of the drainfield is to deliver
wastewater to the soil. The soil purifies the wastewater
by removing the germs and chemicals before they reach
the groundwater or any adjacent surface waters such as
rivers, lakes and estuaries
What Happens In The Drainfield And The Soil?
The real treatment of the wastewater occurs in the soil
beneath the drainfield. Sewage effluent flows out of the
tank as a cloudy liquid that still contains many
disease-causing germs and environmental pollutants.
Effluent flows into the perforated pipe in the trenches,
passes through the holes in the pipe, and then trickles
down through the gravel to the soil. As the effluent
enters and flows through the soil, many of the bacteria
that can cause diseases are filtered out. Some of the
smaller germs, such as viruses, are absorbed by the soil
until they are destroyed. The soil can also retain
certain chemicals, including phosphorus and some forms
of nitrogen.
Where Can A Septic System Be Used?
Unlike a sewer system, which discharges treated
wastewater into a body of water, the septic system
depends on the soil around the home to treat and dispose
of sewage effluent (figure 3). For this reason, a septic
system can be used only on soils that will adequately
absorb and purify the effluent. If a septic system is
installed in soil that cannot do so, the effluent will
seep out onto the soil surface overlying the drainfield.
In addition to causing an unpleasant smell, this
untreated effluent can pose health problems.
In some cases where the soils to not adequately absorb
the wastewater, the toilets and sinks might not drain
freely. If the soil can absorb the effluent but not
treat it, the sewage may contaminate the groundwater.
What Maintenance Is Needed?
Both the septic tank and the drainfield must be properly
maintained. With conscientious maintenance, the system
should work correctly for many years. Such maintenance
begins with water use and waste disposal habits. Since
your family will determine which materials enter the
system, you should establish rules for proper use and
maintenance. The following suggestions will save you
anguish and money when applied to most systems:
Do not put too much water into the septic system;
typical water use is about 50 gallons per day for each
person in the family. Do not wash several loads of
laundry in the same day. It is best to spread the loads
out throughout the week to avoid oversaturation of the
drainfield.
Do not add materials (chemicals, sanitary napkins,
applicators and so on) other than domestic wastewater.
Restrict the use of your garbage disposal.
NEVER pour grease or cooking oils down the sink drain.
Be familiar with the location of your tank and
drainfield area.
Periodically have the solids pumped out of the septic
tank.
Maintain adequate vegetative cover over the drainfield.
Keep surface waters away from the tank and drainfield.
Keep automobiles and heavy equipment off the system.
Do not plan any building additions, pools, driveways or
other construction work near the septic system.
How Will I Know When To Pump The Tank?
After a few years, the solids that accumulate in the
septic tank should be pumped out and disposed of at an
approved location. If not removed, these solids will
eventually overflow, accumulate in the drainfield, and
clog the pores in the soil.
This blockage severely damages the drainfield. While
some clogging of soil pores slowly occurs even in a
properly functioning system, excess solids from a poorly
maintained tank can completely close all soil pores so
that no wastewater can flow into the soil. The sewage
effluent will then either back up into the house or flow
across the ground surface over the drainfield. If this
happens, you may need to construct a new drainfield on a
different part of your lot. Pumping the tank after the
drainfield has become completely clogged will NOT
rejuvenate the system. It will provide only a few days
reprieve until the tank fills up again.
Outlet filters should be removed, cleaned, and replaced
when a tank is pumped. We recommend having your tank
pumped every 3 to 5 years. However, the frequency with
which you will need to pump depends on the size of your
tank, the volume of wastewater, and the solids content
of your wastewater.
What Should Not Be Put Into The Septic System?
Make sure you are aware of the types and amounts of
extra waste materials that are poured down the drain.
Limiting the use of your garbage disposal will minimize
the flow of excess solids to your tank. Garbage
disposals usually double the amount of solids added to
the tank, which increases the need for more frequent
pumping.
Do not pour cooking greases, oils, and fats down the
drain. Grease hardens in the septic tank and accumulates
until it clogs the inlet or outlet. Grease poured down
the drain with hot water may flow through the septic
tank and clog soil pores completely.
Pesticides, paints, pain thinners, solvents,
disinfectants, poisons and other household chemicals
should not be dumped down the drain into the septic
system because they may kill soil microorganisms that
help purify the sewage. Also, some organic chemicals
will flow untreated through the septic tank and the
soil, thus contaminating the underlying groundwater.
Are Septic Tank Cleaners Necessary?
NO. These products include biologically based materials
(bacteria, enzymes and yeast), inorganic chemicals
(acids and bases) or organic chemicals (including
solvents). They do not reduce the need for regular
pumping of the septic tank. Some of these products
contain organic chemicals and may even damage the
drainfield or contaminate the groundwater and nearby
wells.
Is Special Care Needed For The Drainfield?
Yes, The drainfield DOES NOT have an unlimited capacity.
The more water your family uses, the greater the
likelihood of problems with the septic system.
Water conservation practices can help reduce the amount
of wastewater generated in the home. Periodically check
your plumbing for leaky faucets and toilets. Uncorrected
leaks can more than double the amount of water you use.
Many soils that can absorb the 200 to 250 gallons of
sewage usually produced each day by a family of four
would become waterlogged if an extra 250 gallons were
added.
What About Alternatives To The Conventional System?
Other types of septic systems are sometimes used on
sites where the soil is not suitable for a conventional
system. Lots are evaluated on an individual basis. A
perc test or soil report is required on all lot
applications submitted.
Summary – The septic system is an efficient, inexpensive
and convenient method for treating and disposing of
household wastewater. Septic systems will adequately
absorb and purify wastewater if they are properly
maintained. A few precautions can save you anguish and
money. Reducing water use, avoiding grease, pumping the
tank periodically, and properly landscaping the yard to
keep surface water away from the tank and drainfield are
inexpensive precautions that can help assure your system
a long life.
Are Septic Tank Cleaners Necessary?
NO. These products include biologically based materials
(bacteria, enzymes and yeast), inorganic chemicals
(acids and bases) or organic chemicals (including
solvents). They do not reduce the need for regular
pumping of the septic tank. Some of these products
contain organic chemicals and may even damage the
drainfield or contaminate the groundwater and nearby
wells.
Is Special Care Needed For The Drainfield?
Yes, The drainfield DOES NOT have an unlimited capacity.
The more water your family uses, the greater the
likelihood of problems with the septic system.
Water conservation practices can help reduce the amount
of wastewater generated in the home. Periodically check
your plumbing for leaky faucets and toilets. Uncorrected
leaks can more than double the amount of water you use.
Many soils that can absorb the 200 to 250 gallons of
sewage usually produced each day by a family of four
would become waterlogged if an extra 250 gallons were
added.
What About Alternatives To The Conventional System?
Other types of septic systems are sometimes used on
sites where the soil is not suitable for a conventional
system. Lots are evaluated on an individual basis. A
perc test or soil report is required on all lot
applications submitted.
Summary – The septic system is
an efficient, inexpensive and convenient method for
treating and disposing of household wastewater. Septic
systems will adequately absorb and purify wastewater if
they are properly maintained. A few precautions can save
you anguish and money. Reducing water use, avoiding
grease, pumping the tank periodically, and properly
landscaping the yard to keep surface water away from the
tank and drainfield are inexpensive precautions that can
help assure your system a long life.
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