Manufacturers should provide the following specifications regarding the qualities and features of their septic tanks: size, location, retention time, leach or drain field size, and specifications for the standard leach field trench. Some of these specifications require an assessment of the soil properties at the installation site.
Tank size and location specify not only the physical dimensions of the tank itself but should also clarify the material used to construct the tank. Most jurisdictions require a tank size of at least 1000 gallons with a concrete, polyethylene or fiberglass construction. Septic tank location includes information regarding septic clearance distances as well as well clearances; both distances are a consideration when planning the tank installation location.
The septic tank's retention time refers to the amount of time that effluent, or liquid waste, remains in the tank before progressing into the absorption system or leach field. This number is important as a tank must allow sufficient time for solids to filter out of the liquid and either become floating scum or sink to the sludge layer at the bottom of the tank.
The leach field trench specifications and drain field size largely depend on the properties of the soil surrounding the tank. Septic soil tests indicate the ability of the particular soil at a site to absorb septic effluent. However, the leach field trench size is considered somewhat standard, regardless of soil type.