Types of Systems
Sewage enters the pit through the building sewer. The liquid level in the pit rises while water is added. The water level drops as water flows out of the cesspool and into the surrounding soil. Cesspools are normally quite deep, and the pressure from the water column within the pit forces water through the openings into the soil.
Septic Tank and Effluent Disposal System —
As sewage enters the tank an inlet baffle directs the inflow towards the bottom of the tank. Solids settle to the bottom of the tank and form a sludge layer. Grease, soap and other floatables rise to the surface and form a scum layer. An outlet baffle extends down into the clear liquid between the sludge and scum layers.
When sewage enters the tank, an equal volume of water is displaced. This water (septic tank effluent) flows up through the outlet baffle and out of the tank to a disposal system.
The disposal system may include a seepage pit, disposal bed or disposal trenches. The disposal system allows effluent to seep into the soil and away from the septic system. A seepage pit is constructed similar to a cesspool in that openings in a tank or stone lined pit allow effluent to flow out in to the soil. Disposal beds and disposal trenches use a distribution box or pressurized manifold to evenly proportion the effluent amongst perforated laterals that allow effluent to flow out of the system and into the surrounding soil.