septic system general information
SEPTIC SYSTEM GENERAL INFORMATION
The life expectancy of your septic system will be enhanced with knowledgeable soil
testing, site specific design, quality installation, and regular maintenance. Failing septic
systems lower property values, cause health risk, and are generally a serious nuisance.
The Wood County Private Sewage System Ordinance #702 requires proper maintenance
for your septic system. Protecting your investment with good maintenance will ensure
that you as owner can avoid costly repairs in the future. The most important reason to
complete septic system maintenance is to keep your family and the environment safe by
preventing harmful pathogens and bacteria from entering the water table or ground
surface.
Septic Tank: Waste water flows from the house to the septic tank. The tank is designed
to retain waste water and allow heavy solids to settle to the bottom. These solids are
partially decomposed by beneficial bacteria to form sludge. Grease and light particles
float, forming a layer of scum on top of the waste water. Baffles installed at the inlet and
outlet of the tank help prevent scum and solids from escaping. Newer septic tanks have
filters installed at the outlet that need periodic cleaning. The manhole over the filter is
above ground so the filter can be serviced. Septic systems that were permitted after July
1, 2000, must follow the management plan approved with the permit for proper servicing.
Wisconsin State Code requires at minimum the septic tank to be pumped when the
combined sludge and scum layer is equal or greater than 1/3 the tanks liquid level. Wood
County PSSO #702, requires all septic systems to be inspected at least every 3 years.
Drainfield: The clarified sewage is called effluent. This effluent slowly flows by
gravity to one or more perforated pipes that are laid within gravel. Modern drainfields
may have polystyrene bundles or leaching chambers used for waste water storage prior to
soil absorption. The soil is the secondary portion of the treatment process. The soil
below the drainfield filters solid particles and disease causing bacteria. Beneficial soil
bacteria destroy many of the toxins and pollutants while other toxins and pollutants
become bonded to soil particles. Proper soil testing is crucial to ensure unsaturated
conditions beneath a drainfield. It is the unsaturated conditions that will allow the soil
to remove harmful bacteria and viruses. The purified waste water then is either recycled
into the ground water or evaporated back into the hydrologic cycle. This process makes
septic systems one of the most efficient and environmentally friendly ways to treat
domestic waste water.
Mound and Alternative Methods: These systems are used in areas where the site is not
suitable for conventional septic systems. For example, the soil may have too much clay to
allow the water to seep through at the proper rate, or the water table may be too close to
the ground surface. In these systems, the waste water flows from the septic tank to a
pump tank or dose tank. The liquid is then pumped from the dose tank to perforated PVC
pipes buried within a mound or sand filter blanket built on the original soil surface. This
system provides a layer of suitable soil thick enough to ensure adequate time and distance
for proper treatment of the waste water. This is particularly important in areas with high
water tables. Aerobic Treatment Units are available to polish or pre-treat the waste water
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before it enters a mound or drainfield. These units are usually positioned after the septic
tank and before the dose tank. Some units are being used to rehabilitate failing
drainfields that have bio-mat clogging which forms in saturated/anaerobic conditions.
The aerobic units by code can offer one foot of treatment and cut the size of a mound or
drainfield nearly in half. These are particularly valuable on small lots with limited space
available. The aerobic units are a mechanical unit that can add expense to a project.
Holding Tank: The most expensive alternative to on-site treatment is a holding tank. A
holding tank is a large state approved storage tank which collects all the waste water.
Whenever the tank(s) fill the waste water must be pumped out by a licensed Septage
hauler and transported away for treatment. There is either an illuminated or audible
alarm that alerts the owner when a 10% reserve capacity in the last tank is achieved. The
holding tank agreement that is recorded with the property deed details the legal
obligation of the home owner to maintain service properly. Currently Wood County is
using an electronic tracking data base called Carmody. Wood County PSSO #702
requires the licensed Septage haulers to report service to the electronic data base within
30 days of pumping. Our office tracks the holding tank sites to make sure accurate and
legal maintenance is completed. Holding tanks cost less than a mound system to install,
but annual pumping and hauling cost can be substantial.
Signs of System Failure: Septic systems generally give little warning that they are about
to fail. However, the following symptoms often indicate that the system is becoming
clogged:
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Sewage odor near the septic tank, or drainfield.
Fixtures and toilets backing up or draining more slowly.
Sewage on the ground or over the drainfield as indicated by wet spongy ground or
ponding of a grayish black liquid.
The ponding of sewage on to the ground surface or roadside ditch is considered a human
health hazard and is prohibited by both Wisconsin State Statues and Wood County
Ordinance. The Licensed Professionals completing the septic system inspections are
also required by law to report failing systems to the Planning and Zoning Office.
Replacement Orders are issued from our office with a specific deadline for correction. If
the deadline is not met then enforcement through Circuit Court may be required. (See
Figure 1 @ Bottom Page)
Septic System Protection: Following these simple guidelines and procedures can help
your septic system to recycle waste water properly and have a long life:
 Practice water conservation, fix leaks and drips, and install “low flow” fixtures
when replacing old plumbing.
 Do not overload the system. Early morning and bedtime are peak water use
times. Run dishwashers and washing machines at other times of the day. Do not
do all of the laundry in one day.
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 Do not dispose of the following into a septic system: coarse organic matter-
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vegetable trimmings, coffee grounds, cigarette butts, tampons, diapers, condoms,
baby wipes, etc. These will clog the septic tank with sludge and will require more
frequent tank pumping. Use of a garbage disposal may shorten a drainfield life.
Home composting is an excellent alternative.
Fats and grease – cooking oil, bacon grease, etc., will bypass the tank baffles and
clog the drainfield.
Chemicals such as pesticides, disinfectants, motor oil, acids, medicines, paint and
paint thinners, etc. will kill the good bacteria that decomposes organic matter in
the tank, and cause increased sludge build up. This septic tank will become filled
with high strength waste water and create anaerobic conditions in the drainfield
causing a Bio-mat, or clogged soil.
Avoid compacting the soil over the drainfield area. Compaction may decrease the
soil loading rate causing the waste water to pond on the ground surface. Do not
drive vehicles or build structures over either the septic tank or drainfield. These
activities may cause cracks in the piping or tanks.
Do not plant deep rooted trees or shrubs over the drainfield. Deep rooted water
loving plant species have roots that will plug pipes and fill tarred joints in the
septic tank. These roots cause physical damage and plug the drainfield.
Saturated Conditions
Intestinal viruses and harmful
bacteria may be transmitted
indirectly by vectors or water.
Well
Untreated
Sewage
BOD
TSS
Bacteria
Viruses
Saturated
anaerobic
zone = no
treatment
Nutrients
Groundwater
Figure 1.
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