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Over 300,000 homes in New Jersey use private onsite wastewater treatment systems, which are commonly referred to as septic systems. When properly designed, installed, and maintained, these systems have little adverse effect on the environment in areas with low population densities.

Septic systems provide the benefit of recycling used water. First, the water is filtered, and then it is recharged to ground water supplies, which are now seriously depleted in some areas in New Jersey. However, in areas with high population densities, septic systems can contribute to contamination of ground water and wells. A key problem with septic systems is a misunderstanding of their function and purpose. Septic systems are only designed for the treatment of sanitary waste. They are not intended for the disposal of household waste or other chemicals.

Proper maintenance is crucial to keep a septic system working. Septic system owners are unique in that, unlike homeowners in areas served by a municipal sewer department or a regional sewerage utility authority, these owners are solely responsible for the daily operation and maintenance of their personal wastewater treatment and disposal system. While this may sound like a big job, many septic owners find living with a septic system easy.



Septic systems have several main components: a septic tank, a distribution network and an absorption area. Some septic system designs have other parts. Advancements in onsite wastewater treatment system technology have changed the conventional septic design greatly. Often new onsite technology is capable of producing a higher quality effluent and better pollution control than older systems.

Typically, the first component of a septic system is a septic tank. This large, buried, watertight container is usually prefabricated from concrete, fiberglass or polyethylene. It receives wastewater from your bathroom, kitchen and laundry room. The septic tank holds the wastewater for a long enough time to allow the heavy solid particles in the wastewater to settle to the bottom of the tank and the light materials (like oil and grease) to float to the water surface. These materials become sludge and scum.

Bacteria in the system help to break down organic matter in the wastewater. This process requires time. With the "floaters" and "sinkers" remaining in the septic tank, the resulting liquid, now known as effluent, will flow out from the septic tank into the distribution system.

The distribution system provides the means by which effluent is conveyed from the treatment tank into the absorption area. The distribution system may consist of a gravity delivery line to a distribution box, or to a tank with a lift or dosing pump, or to a siphon chamber.

The last component of the distribution network is the disposal field or absorption area. This generally consists of a set of perforated distribution pipes, which are installed in either subsurface trenches or beds. The distribution lines, sometimes called laterals, are designed to disperse the effluent over the entire absorption area. The disposal field removes harmful, disease causing microorganisms, organic chemicals and nutrients while allowing the water molecules to flow downward toward the ground water table.

Treatment of sanitary waste in the septic system is a function of bacteria/viral die-off. For this part of the system to function properly, it must be constructed on suitable soil by a knowledgeable professional.



State and local regulations determine what constitutes suitable soil for the disposal field. These regulations have been developed after careful consideration of many factors that affect a soil's ability to adequately treat domestic wastewater. Foremost among these is the speed with which water will flow downwards through the soil. If a soil is too fast or too slow it may not be suitable.

Before a septic system is built, State laws require that a permeability test be performed to determine how fast the soil absorbs water. Soil examination by a professional soil scientist can provide a more reliable assessment of the capacity of the soil to accept wastewater.

When designing a system, your design engineer should check the water table level to be sure it is at least four feet below the bottom of the absorption area. The designer should also make sure the septic system is located a safe distance away from any potable wells or water bodies.

The design and construction of the disposal field is critical to how well your septic system functions. The perforated pipes, or laterals, must be laid in suitable soil, away from tree roots and manmade structures. The dimensions of the disposal field must provide sufficient area and volume to absorb your home's daily wastewater.



If you need to construct, alter or repair a septic system, it is important that you find qualified professionals to do the necessary design and construction work. They are familiar with the Standards for Individual Subsurface Sewage Disposal System.

Problems that occur during construction can cause a septic system to malfunction. These include soil compaction due to excavation at times when soil temperature is high, pipes laid on improper grades, incorrect joints and alignments between system components and pipes broken or crushed during the building process.



In densely populated areas, the accumulation of nitrates from septic systems in ground water may cause health problems. Nitrate is oxidized nitrogen, which can interfere with the blood's ability to carry oxygen, particularly in infants. Nitrate concentrations in excess of 45 parts per million have been reported to cause methemoglobinemia in infants ("the blue baby syndrome"), an illness in which the infant's coloring takes on a bluish cast. The illness is rare and easily reversible once diagnosed. However, it is not fully known what health effects result from long-range exposure to low levels of nitrates.

If you rely on a well and septic system, have your well water tested periodically for nitrates, in addition to the other constituents recommended by the safe drinking water program. Use a relatively inexpensive test to ensure that the nitrate level is less than the Maximum Contaminant Level allowed under the State's standards for Safe Drinking Water (10 parts per million).



Your septic system can be compared to a small wastewater treatment plant in your yard. It treats your wastewater using a combination of physical, chemical and biological processes. Therefore, to avoid problems, it is important that you ensure that all of these processes function properly.

An onsite wastewater treatment system that is not functioning properly can release disease-causing microorganisms and unpleasant odors that can offend your neighbors. The principal signs of septic system problems are easy to detect: effluent rising to the ground or drains and toilets that operate sluggishly or not at all. Septic system problems can be minimized or avoided by understanding the needs and limitations of your system and by observing several precautions.



Toxics and Motor Oil
Toxic and household hazardous chemicals should never be disposed of through your septic system, as these can disrupt its functioning and contaminate ground water. Such chemicals include paints, varnishes, pesticides, solvents and drain openers. (See the Household Hazardous Waste Chapter in this booklet on proper disposal of these chemicals

Likewise, used motor oil from your car or truck should not be disposed of in a septic system. It should be recycled by taking it to your nearest recycling center or a service station.

Household Products
Inert or non-biodegradable materials should not be disposed of through your septic system. Examples are cat box litter, disposable diapers, coffee grounds, sanitary napkins and paper towels. These items can quickly fill your septic tank, decrease its efficiency and will require more frequent pumping of your tank.

Large quantities of cooking grease, oil and fats should not be allowed into septic systems. These can contribute to blockage within the system. The use of garbage disposal units should be avoided, as these increase the amount of solids in the septic system, and thus require more frequent pumping.

Water Everywhere
Too much water use can compromise your septic system's capability to treat and dispose of wastewater. Excessive water coming into the disposal field can result in hydraulic overloading and a reduction in infiltrative capacity. Excess volumes of water entering the septic tank can affect its ability to retain solids and result in carry-over and clogging within the disposal field.

The performance of your septic system will be improved if you cut down on water use so that a smaller volume of wastewater passes through the system. Water-saving showerheads can be easily installed and may reduce both your water use and heating bill. Be careful to turn taps off when not in use and repair or replace leaking faucets.

Your absorption area (drain field) will not work well if there is too much water in the soil. Water drained from basement floors, footings or roofs should be directed away from the disposal area to some other area in your yard. Your yard surface should be graded so that stormwater drains away from the septic drainage field and not toward it.

Consideration should be given to distributing dish washing and laundry throughout the week, instead of all at once during one or two days. It would be better to avoid showering and bathing at times when dishwashers and laundry are in use.




It is important to maintain a diagram of the location of all components of your septic system including the septic tank, any connection lines and pipes, distribution boxes and disposal field. For newly constructed septic systems, a copy of the design plans should be available. For older existing systems, simply diagramming the location to septic system components, measured from a common point on the building, is adequate.

When you are aware of the location of septic system components, accidental damage resulting from machinery and excavating tools can be prevented. Moreover, ready knowledge of the location of septic system components facilitates maintenance and repairs or alterations when necessary.

Be sure your septic system is inspected and pumped out on a regular basis. Remember that toxic gases can accumulate in septic systems, so use extreme care when inspecting it. At least annually observe the liquid levels through all of the inspection ports. Tank inspections can be dangerous, so consider employing a professional to do the inspection.

Have a reputable contractor pump out the tank to remove the accumulated sludge and scum every two to three years. This helps ensure that there is enough space in the tank for wastewater and prevents solids from escaping into the absorption system.

There is no known substance capable of eliminating or reducing the buildup of sludge and scum that makes periodic pumping unnecessary. Do not put chemical in your septic system for treatment or maintenance.

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  • Know the location of all components of your septic system.
  • Keep heavy vehicles away from the system, so as to avoid crushing or compacting any part of it.
  • Direct water from the roof, down spouts, footing and basement drains away from the disposal field.
  • Pay attention to what goes down your drain!
  • Dispose of hazardous chemicals properly. Do not pour them down the toilet or drain. They can destroy the bacteria in your septic system and contaminate local ground water.
  • Don't use garbage disposals. They contribute unnecessary solids and grease to your septic system.
  • Conserve water whenever and wherever possible.
  • Don't use toilets as trash cans. Dispose of solid waste in your garbage.
  • Maintain a permanent written record of all septic tank pumping, inspection, repairs or alterations to your septic system. The name of the hauler, contractor or professional engineer who performs the work should be retained in the event that it is necessary to contact them in the future.
continue to Chapter 9: Household Hazardous Waste
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Last Updated: July 11, 2018