What is the primary function of the drain field in a septic system?

The primary function of the drain field, also known as the leach field or soil absorption field, in a septic system is to allow effluent to disperse into the soil for further treatment. After wastewater from the septic tank has undergone initial treatment—where solids settle to the bottom and scum rises to the top—the liquid effluent is then transported to the drain field.

In the drain field, the effluent seeps into the soil, which acts as a natural filter. The soil microorganisms help to further break down and treat the effluent, removing harmful pathogens and nutrients through biological, physical, and chemical processes. This dispersal and subsequent treatment are essential for protecting groundwater and surface water from contamination, making the drain field a critical component of the overall septic system.

The other options do not align with the primary function of the drain field. For example, the drain field is not designed to store wastewater or collect rainwater runoff. Its role is specifically focused on the safe dispersal and treatment of effluent to ensure environmental safety and sanitation.