An onsite wastewater treatment disposal system is designed to be environmentally safe and to protect public health. A properly installed and operated system treats wastewater from your home and returns it to the groundwater to enhance and protect our groundwater resources. Successfully used for over 100 years, nearly one-third of the United States' population use this method of wastewater treatment!
This webpage provides you with the essential information and guidelines for operation and maintenance of your system. By carefully reading and following these guidelines, you will have many years of trouble-free service, while at the same time protecting our environment. We recommend keeping a folder for all of the information on your septic system, including your permit, site drawings, descriptions of maintenance and repairs performed and other important documents.
The first component in the system is a septic tank that uses natural processes to treat the wastewater generated in your home. The second component is a drainfield or subsurface infiltration field that recycles the treated materials. The system accepts both "blackwater" (toilet wastes) and "greywater" (wastes from the kitchen sink, bath and showers, laundry, etc.) Water that should not be discharged to the system includes water from foundation or footing drains, roof gutters and other "clear" water.
The septic tank provides the first step in treatment. Its primary purpose is to protect the drainfield or other system components from becoming clogged by solids suspended in the wastewater. The wastewater discharged from the home goes directly into the tank where it is retained for a day or more. During the time it is in the tank, the heavier solids settle to the bottom to form a sludge layer. The lighter solids, greases and oils float to the top to form a scum layer. In addition to acting as a sedimentation chamber, and providing storage for the sludge and scum, the septic tank also digests or breaks down the waste solids. Anaerobic and facultative micro-organisms that thrive without oxygen feed on the solids to reduce the volume of sludge and scum. In the process, carbon dioxide, hydrogen sulfide and other gases are produced which must be vented from the tank through the plumbing vent on the roof. Only about 40% of the sludge and scum volume can be reduced in this manner, however, so the tank must be pumped regularly to remove the accumulated solids. If not done the tank will fill with sludge and the solids will be washed out into the drainfield where they will quickly clog the soil.
The drainfield provides final treatment of the wastewater and disposes the treated water through groundwater recharge. The drainfield is typically built as a series of trenches or as one larger bed, and is usually 1 to 3 feet below ground level. The drainfield must be constructed in permeable soils, have a level bottom, and be 2 or more feet above the groundwater table. While there are many types of drainfield systems, we will describe here a conventional gravel and pipe system.
The excavated trench or bed is filled with 6 to 12 inches of gravel. The gravel exposes a soil infiltrative surface and provides storage for the wastewater, A perforated pipe is laid over the gravel to distribute the partially treated liquid, called effluent, from the septic tank over the bottom of the drainfield. The gravel and pipe is covered with synthetic fabric to help keep soil particles out of the system and the area backfilled with soil to cover the system.
The Septic tank effluent is allowed to flow to the drainfield by gravity or is dosed by pump or siphon. The effluent enters the soil and is treated as it percolates to the groundwater. The soil acts as biological filter to remove nearly all harmful substances including disease-causing bacteria and viruses, toxic organics and other undesirable wastewater constituents remaining in the septic tank effluent.
Drainfields other than those described above can be used such as at-grades, mounds, and drip distribution. There are also substitute medias that can be used in place of the gravel.
Your onsite treatment system represents a significant investment which you will want to protect. "An ounce of prevention is worth a pound of cure" was never more true than it is with onsite system care. With proper operation and regular maintenance, your system will function better and last longer. Committing a little attention to the care of your system is the best way to avoid the nightmare of a failing system. Read and follow the Dos and Don'ts for trouble-free operation.
"It was a pleasure working with you. You and Dylon did a great job. On time, on budget, and exceeded my expectations. I am very satisfied with the work you did."