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Septic Systems & Soil Types

A septic tank is used for households and other buildings when they do not have access to local sewer lines. A septic system consists of a tank, a drain field and the soil beneath the drain field. The type of soil, the height of the ground water table and the soil's ability to drain will dictate what type of septic system will be used.

  1. Coarse Sand and Gravel

    • The pressure distribution septic system is used in coarse sand soils and gravel. The pressure system is different from a typical septic system in that the septic pump chamber is located between the tank and the drain field. The pump chamber stores wastewater or effluent until its levels reach a predetermined amount. Once it is high enough, the pump is triggered to activate and it pumps out the effluent into the drain field. Since it is pressurized, it is sent out of the perforated pipes with such force that it saturates the drain field quickly; it works much like a sprinkler does, except it's underground.

    Fine Sand and Loam

    • Soils that drain well, such as sand and loam, typically will have the traditional concrete septic tank system with a common drain field. In this septic system, a solid pipe leads from the tank to a distribution box, where it is then sent to two or more perforated pipes, which leach the water out into the soil.

    Impermeable Soils

    • Bedrock, a high ground water table or soils that do not drain well, such as thick clay soils, use a sand mound septic system. In this system, the septic tank is connected to a storage tank. The wastewater is sent from the home to the septic tank and then to the storage tank. Near the storage tank, perforated PVC pipes are buried above ground in a mound of sand. The mound of sand is covered by geotextile fabric, which is in turn covered by topsoil and grass or other vegetation. The wastewater runs from the storage tank to these pipes, where it is safely released into the sand to be processed by bacteria. The water seeps into the sand and slowly evaporates or is taken in by plant roots.

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