There are three main categories of septic systems, including the standard gravity, pressure distribution and advanced treatment. Within these categories there can be different variations and set-ups available depending on the area and the regulations in the area where the tank is being installed.
Conventional or traditional systems make up the first two types of septic systems. The gravity and pressure styles are the most common. They are made up of drainage fields, septic tanks, gravel, soil and some method of moving waste from the home to the tank. This is normally a pipe of some sort. The main variations come in the advance treatment systems.
The advance treatment systems come in a wide variety, such as mound systems, drip irrigation systems, recirculating sand systems, chlorine disinfection systems and evapotranspiration systems. Mound systems are used where there may not be enough soil for a regular system. The waste is directed to the top of a mound where it is forced to flow through more dirt, thus filtering it more before it hits any kind of ground water. Some of these advance treatment systems can only be used in specific areas. Evapotranspiration systems are only ideal for the Southwest because the amount of evaporation exceeds the amount of rainfall. These systems also require a pre-treatment tank to be used.