Onsite Wastewater

A septic tank system consists of a large, watertight tank that receives wastewater from the home plumbing system. The tank is followed by an underground drain field consisting of a network of perforated pipe and drainage media or chambers for distributing partially treated water from the septic tank to the soil for final treatment and disposal.
CivicSend Slideshow Left Arrow Slideshow Right Arrow
How It Works
Septic tanks contain bacteria that grow best in oxygen-poor conditions. These bacteria carry out a portion of the treatment process by converting most solids into liquids and gases. Bacteria that require oxygen thrive in the drain field and complete the treatment process that begins in the septic tank. If the septic tank is working well, the wastewater which flows out of the tank is relatively clear, although it still has an odor and may carry disease organisms.

Operation & Maintenance
After the septic tank system is placed in service, proper operation and maintenance of the system will ensure continued efficient service and prevent sudden replacement expenses. The septic tank and drain field are designed and installed to handle a maximum calculated daily sewage flow. Consistently exceeding the design flow will eventually overload the system and cause failure.

Products
The ta
nk may receive new solids faster than it can treat them and the drain field may become saturated from excessive water use. Various products are on the market which are said to start, accelerate, or improve the action in the septic tank. Since all necessary bacteria are already present in the sewage entering the system, such products are not recommended.

Pumping & Inspections
Maintenance of a septic tank will depend largely on the daily sewage flow and individual household wastewater characteristics. With ordinary use and care, a septic tank should not require pumping out more than once every three to five years. It should, however, be inspected to determine the depth of accumulated sludge and grease.

Garbage Disposal Waste

Waste from a kitchen garbage disposal unit puts an extra load on a septic tank system. If a garbage disposal is used, the capacity of the tank should be increased to handle the increased solid wastes. The tank may also require more frequent pumping to remove accumulated solid waste buildup.

Drain Field Overflow

Failure to pump out a septic tank system when indicated will result in solids or greases overflowing into the drain field, which in turn may become clogged and stop functioning. In this event, not only will the tank have to be pumped out, but the drain field may also have to be replaced. Septic tanks can only be pumped by certified septic tank cleaning firms permitted by the NCDENR Division of Waste Management.

Location
Contaminants can travel long distances in some soils. Therefore, drinking water wells should be located at least 100 feet from any part of a septic tank system, except in situations where space limitations and other site-planning considerations allow a reduction of up to 50 feet.

Preventing Failures
Septic tank systems fail when the drainfield does not dispose of sewage as rapidly as it is being added to the system. Thus, improvements that reduce the amount of incoming water or improve the quality of wastewater passing through the system will increase the system's longevity. Other important considerations include the following: 

A drainfield can be damaged by compaction due to vehicular traffic and can be blocked by excessive shrubbery or tree root growth. The drainfield should be unobstructed and seeded with grass. Grass and sunlight aid evaporation.
Washing machines are responsible for large volumes of water entering the septic tank. The surge of wash water can create turbulence in the tank which increases the amount of solids flushed into the drainfield. Space washings throughout the week rather than doing many loads at a time.
Cooking oils and grease are trouble makers. The type of bacteria found in septic tanks and drainfields do not survive or function well in solidified grease. Grease and cooking fats should never be washed down the sink drain. Save grease in jars or cans for disposal in the garbage.

Do...
Know the location and capacity of your septic tank system. If you have a copy of your original permit, keep it available for future reference.
Have tank pumped when the combined depth of the sludge and scum equals 1/3 of the tank liquid volume.
Install the system so that rainfall and surface water will flow away from the drainfield. · Grow grass above the system.
Install water conservation fixtures or devices to reduce the total volume of water entering the system.
Keep plumbing fixtures such as toilets and faucets in good repair to prevent leakage and wasting of water
Keep copies of maintenance receipts

Don't...
Never flush paper towels, newspapers, wrapping paper, rags or sticks into the system.
Never over-use ordinary household cleaning chemicals that will be flushed into the system.
Never pour out or empty hobby or home industry chemicals into the system.
Never allow grease or other bulky waste to enter the system.
Never flush toxic materials such as pesticides into the system.
Never plant trees or shrubbery in the drainfield.
Never allow vehicles (cars, trucks, etc.) to drive across or park on the drainfield. (Protect it from being crushed.)
Never waste water.
Never use chemical solvents to clean plumbing lines or a septic tank system.