What is the primary function of a septic tank?

The primary function of a septic tank is to provide primary treatment of wastewater and to create anaerobic conditions that facilitate the breakdown of organic material. In a septic tank, solid waste is settled to the bottom and begins to decompose under anaerobic conditions—meaning without oxygen. This process helps in reducing the volume of solids and converts some of the organic material into simpler substances. The clarified wastewater, or effluent, then flows out of the tank to a drainage field where further treatment and filtration occur through soil.

While filtration of wastewater and distribution of treated effluent are important aspects of a complete septic system, they are not the primary function of the septic tank itself. Filtration typically occurs in the soil after the effluent leaves the septic tank, and distribution is managed by the drain field. Complete wastewater treatment involves multiple steps and components that occur after the septic tank has done its part. Thus, the septic tank's role is centered on primary treatment and facilitating anaerobic conditions for effective waste breakdown.