Every septic tank (except the cesspool) has two distinct components: Septic Tank to catch solids and Leach Field to dispose of liquid. Cesspools permit direct discharge of sewer (solids and liquid) into a pit, pond or perforated tank where effluent evaporates and leaches down right into surrounding soil while solids remain behind. Septic tanks use one of seven treatment area designs to deal with effluent:
Leach Pits are huge gravel filled holes, preferably with a perforated tank in a center for discharging effluent. Drywells are a passive (no pump) option for small/odd lots where a long leach field percolation field is not possible or wanted. Leach pits benefit from surface around sides of the hole to dispose of huge quantities of water in the right soil types. Adding a drywell to a leach pit offers it additional ability to accept large surges at once. Always enable at least 8 or 10 feet of undisturbed soil space between pits to ensure maximum percolation and effluent treatment.
Leach Fields are trenches (or rectangular beds) dug in yard and loaded with a foot of 3/4" - 1-1/2" crushed rock and a 4 inch diameter perforated pipe. The pipe-in-gravel leach line is covered with geotextile fabric (landscape weed barrier) and afterwards backfilled with a foot or 2 of native soil atop. Gravity sends out effluent to leach field with at least a 1/8 inch per foot drop then is spread into soil evenly with all the leach field perforated pipe being at the same level.
Chamber Systems are arched panels in the trench, which really advance leach field design. Effluent flows into this big open area beneath the lawn; the whole bottom of a chamber is open. With no gravel inside, chambers have enough air to help keep the leach field soil aerobic and healthy.
Pressurized Mound Systems use an electric pump to force effluent right into elevated mound 'constructed soil' systems and distant trenches, beds or chambers. Even distribution of effluent is key to smaller sized leach fields as well as better treatment of the waste water. Poor soil percolation sites typically need distribution constructed sand mounds with two inch diameter pipe drilled with 1/4 inch holes every two feet, or so.
Evapotranspiration/ Drip Beds are pressurized systems with smaller sized holes or nozzles (drip) for more uniform distribution of waste water, however are prone to plugging from calcification of the nozzles. In locations that do not obtain snow cover in the winter season, long shallow trenches could be gone through yard, sending waste water right into the root zone near surface area. The plants transpire water through growth and also some water vaporizes being so near to surface, with a smaller portion of effluent percolating down into water table.
Lagoons, Cesspits and Cesspools are artificial ponds where the effluent percolates and evaporates, typically assisted by a fountain or bubbler. Generally reserved for high clay soil areas where percolation is tough, shallows can be lined to prevent percolation in a fragile location - evaporation being the only ways of disposal. 6 foot fencing as well as a locked gate are common practice with any kind of lagoon or cesspool due to the legal responsibility from security issues.
Constructed Water Treatment Wetlands are shallow lagoons and generally developed in warm climates considering that plant life is essential. Active plant growth year-round is preferred for the built wetland plants in order to help dissipate the nitrogen as well as really treat the effluent. Created wetlands reveal one of the most guarantee for a carefree low-maintenance therapy area, yet you do generally have to stay in a non-freezing climate. They are a superb selection for greywater disposal, taking a major load off the septic tank and leach field system (blackwater only - toilets and dishwasher).