Properly Managing Your Pressure
Distribution System |
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 Septic tanks with gravity
flow drainfields have been used for many years in areas not served by public
sewers. Unfortunately, not all soil and site conditions are well-suited
for conventional septic systems. To protect public health and water quality,
alternative systems are often used in areas where conventional systems cannot
guarantee safe sewage treatment. The pressure distribution system is one
such alternative. It provides:
- Dosing and resting cycles.
- Uniform distribution of effluent.
- Shallow placement of the drainfield.
The following information will help you understand your pressure distribution
system, and keep it operating safely at the lowest possible cost.
A typical pressure distribution system has three working parts:
- The septic tank.
- The pump chamber with the pump.
- The drainfield with its replacement area.
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| The Septic Tank |
The typical septic tank is a large buried container made of concrete,
fiberglass or polyethylene. Wastewater from your home flows into the tank.
Heavy solids settle to the bottom where bacterial action partially decomposes
them. Most of the lighter solids, such as fats and grease, rise to the top
and form a scum layer.
The wastewater leaving the septic tank is a liquid called effluent. It
has been partially treated but still contains disease-causing bacteria and
other pollutants. From the tank, the effluent flows by gravity to the pump
chamber.
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| Proper Care: |
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Inspect your septic tank once a year and pump it when needed. If the tank
is not pumped periodically, solids escaping from the septic tank will clog
the pump and drainfield. Using a garbage disposal will increase the amount
of solids entering the tank, requiring more frequent pumping. |
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Avoid flushing harmful material into the septic tank. Never put grease,
newspapers, paper towels, cigarettes, coffee grounds, sanitary napkins,
solvents, oils, paint or pesticides into the tank. For information on the
proper disposal of hazardous household waste, call the Recycle Hotline,
1-800-RECYCLE. |
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Avoid using any chemical or biological septic tank additive. Additives do
not improve the performance of the tank. They do not reduce the need for
routine pumping, and some are even harmful to the system. |
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| The Pump Chamber |
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The pump chamber is a concrete, fiberglass or polyethylene container
that collects the septic tank effluent. The chamber contains a pump, pump
control floats, and a high-water alarm float.
The control floats are adjustable and are set for pumping a specific
volume of effluent. When the effluent rises to the level of the ON float,
the pump starts delivering effluent to the drainfield. The pump lowers the
effluent level to the OFF float and stops.
The high-water alarm float in the pump chamber starts an alarm to warn
you of any pump or system malfunction. The float is set to start when the
effluent in the pump chamber rises above the ON float. The alarm should
consist of a buzzer and an easily visible light. It should be on an electrical
circuit separate from the pump.
The pump discharge pipe should have a union or other quick-disconnect
coupler for easy removal of the pump. A piece of nylon rope or other noncorrodible
material should be attached to the pump for taking the pump in and out of
the chamber. |
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| Proper Care: |
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Check the pump chamber, pump and floats every year and replace or repair
worn or broken parts. Pump maintenance should follow the manufacturer's
recommendations. Electrical parts and conduits should be checked for corrosion.
If the alarm panel has a push-to-test button, it should be checked regularly. |
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Install a septic tank effluent filter or pump screen if your system does
not have one. Screening or filtering the septic tank effluent effectively
prevents solids from clogging the pump and drainfield pipes. Inspecting
a screen or filter, and clearing when necessary are quick and easy, and
prevent costly damage from solids entering the system. |
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Take action to protect the drainfield from overloading after a prolonged
power outage or pump failure. Effluent will continue to collect in the pump
chamber until the pump resumes operation. With additional effluent in the
chamber, the pump may dose a volume greater than the drainfield can handle.
If all of the reserve storage inside the chamber is used, the plumbing in
your home can back up. When the pump is off for more than 6 hours, take
the following measures to help protect the drainfield: |
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- Reduce your water use to a minimum.
- Turn off the pump at the control panel.
- After power is restored or pump service is completed, switch the pump
on and let it run for 5 minutes maximum, and turn it off again. Repeat
this manual switching every 6 hours until the effluent drops to the OFF
float level and the pump turns off automatically. If there is little water
use during the problem, the pump may automatically turn off during the
first manual switching.
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| The Drainfield |
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The drainfield is a network of pipes placed in gravel-filled trenches
(2—3 feet wide) or beds (over 3 feet wide) in the soil. Effluent is
pumped through the pipes in controlled doses to insure uniform distribution
throughout the drainfield. The effluent leaves the pipes under low pressure
through small holes, and trickles downward through the gravel where it reaches
the soil. The soil filters and treats the effluent, removing bacteria and
other pollutants before it reaches the groundwater.
Every new drainfield is required to have a designated replacement area.
It must be maintained should the existing system need an addition or repair. |
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| Proper Care: |
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Know where your system and replacement area are located and protect them.
Before you plant a garden, construct a building, or install a pool, check
on the location of your system and replacement area. |
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Practice water conservation and balance your water use throughout the week
to keep from overloading the system. The more wastewater you produce, the
more the soil must treat and dispose of. |
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Divert water from surfaces such as roofs, driveways, or patios away from
the drainfield and replacement area. Soil over your system should be slightly
mounded to help surface water runoff. |
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Keep traffic, such as vehicles, heavy equipment or livestock off your drainfield
and replacement area. The pressure can compact the soil or damage pipes. |
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Landscape your system properly. Do not place impermeable materials over
your drainfield or replacement area. Materials, such as concrete or plastic,
reduce evaporation and the supply of oxygen to the soil needed for proper
effluent treatment. Grass is the best cover for your entire system. |
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Inspect the drainfield and downslope areas periodically for odors, wet spots,
or surfacing sewage. If your drainfield has inspection pipes, check them
to see if there is a liquid level continually over 6 inches. This may be
an early indication of a problem. Call your local health agency for assistance. |
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| What If the Alarm Goes On? |
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If, for any reason, the effluent level inside the pump chamber reaches
the alarm float (due to a faulty pump, floats, circuit, or another problem),
the alarm light and buzzer will start. By using water conservatively (avoid
baths, showers, and clothes washing), the reserve storage in the pump chamber
should allow you enough time to get the problem corrected. To silence the
alarm, push the reset light on the alarm panel. Before calling for service
or repair, check to see if the problem could be:
- A tripped circuit breaker or blown fuse. The pump should have a separate
circuit with its own breaker or fuse. If it's on a circuit with other equipment,
that equipment can cause the breaker to trip.
- A pump or float switch power cord that has come unplugged. If electrical
connections are the plug-in type, make sure that switch and pump plugs
are making good contact in the outlets.
- Control floats tangled by other parts in the chamber such as the electric
power cord, lifting rope, or pump screen. Make sure that floats operate
freely in the chamber.
- Debris on floats and support cable that is causing the pump to switch
off. Lift the floats out of the chamber and clean.
Caution! Always turn off the power supply at
the circuit breaker, and unplug all power cords before handling the pump
or floats.
Do not enter the pump chamber. Gases inside pump chambers are poisonous
and the lack of oxygen can be fatal.
If the problem cannot be located with the above steps, call your pump
service person or on-site system installer for service or repair. The service
of pumps and other electrical equipment must be done by an experienced person. |
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| Additional Information |
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More information is available from the following Department of Health
publications:
Guidelines for Pressure Distribution Systems, 1984.
Understanding And Caring For Your Septic Tank System, DOH 334-009.
Water Saving Guideline 1, DSHS 22-643 (x) 5/88.
Septic Tank System For Your Home, DSHS 22-45A 11/83.
On-Site Sewage System Regulations, DOH 334-006A WAC 246-272.
These are available from your county health agency or by writing to:
Washington State Department of Health
Office of Community Environmental Health
Mail Stop LD-11 Olympia, WA 98504
Other sources of information include your local:
Health Agency
Soil Conservation Service Office
Cooperative Extension Office
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Reprinted with permission from the Washington State Department of Health.
Issued by Washington State University Cooperative Extension and the U.S.
Department of Agriculture in furtherance of the Acts of May 8 and June 30,
1914. Cooperative Extension programs and policies are consistent with federal
and state laws and regulations on nondiscrimination regarding race, color,
gender, national origin, religion, age, disability, and sexual orientation.
Trade names have been used to simplify information; no endorsement is intended.
Published June 1992. Subject code 376. A |
