Septic System Types

Conventional

A conventional system is the most basic of all septic systems. These systems are installed in areas where the soils dictate that the drainfield may be installed right in the ground. There will still be a tank and a drainfield as with all systems. If the drainfield is located in an area which is lower than the tank, the effluent will drain to the drainfield by gravity. If the drainfield is located higher than the tank, there will be a pump in the tank to pump the effluent to the drainfield. This type of system will be called a pumped conventional.

The conventional systems are typically the least expensive to install due to the fact that the drainfield can be made right in the ground.

Mound

A mound system is used in areas where the soils are less than perfect such as a high water table or rocky soil. Such areas do not allow for the three feet of dry soil for filtration so the drainfield is then placed above the ground at a level where the three feet of dry soil is obtained creating the "mound".

The mound system has a two septic tank design. The first tank provides a place for the solids to settle. The second tank contains the effluent; this may also be called the pump chamber. When the effluent level reaches a certain point, the pump kicks on and the effluent is sent out to the drainfield.

Mound systems are typically the most expensive to install due to the fact that the drainfield (or mound) needs to be built versus being able to put the trenches right in the ground.

AT-Grade

An at-grade system is used when the soils are too shallow for a conventional system and the mound would make them too deep.

An at-grade system is similar in design to a mound system. It will still have the normal tank for holding solids and the effluent tank or pump chamber. The drainfield will be built right at the grade of the ground. The drainfield will be visible like the mound but not as high.

The at-grade system is less expensive than a mound due to the fact that the sand that is used to build a mound is not required in an at-grade.

Holding Tank

A holding tank is used in areas where there is no possible way to install a drainfield. Due to the fact that there is no drainfield, everything that is put down any of the drains or flushed in the home will go into the holding tank. The size of the holding tank will be determined by the number of bedrooms in the home. The minimum size is a 2000 gallon tank. One draw back to a holding tank is that it will need to be pumped much more often than a septic tank with any other type of system. How often will depend on how much water is used in the home each day.