Septic System Terminology

The definitions of these terms have been provided by the United States Environmental Protection Agency (EPA).

Conventional Septic System

Definition: A wastewater treatment system consisting of a septic tank and a typical trench or bed subsurface wastewater infiltration system.

Drain Field

Definition: Shallow, covered, excavation made in unsaturated soil into which pretreated wastewater is discharged through distribution piping for application onto soil infiltration surfaces through porous media or manufactured (gravelless) components placed in the excavations. The soil accepts, treats, and disperses wastewater as it percolates through the soil, ultimately discharging to groundwater.

Effluent

Definition: Sewage, water, or other liquid, partially or completely treated or in its natural state, flowing out of a septic tank, subsurface wastewater infiltration system, aerobic treatment unit, or other treatment system or system component.

Effluent Filter

Definition: A removable, cleanable device inserted into the outlet piping of the septic tank designed to trap excessive solids due to tank upsets that would otherwise be transported to the subsurface wastewater infiltration system or other downstream treatment components.

Graywater

Definition: Wastewater drained from sinks, tubs, showers, dishwashers, clothes washers, and other non-toilet sources.

Percolation

Definition: The flow or trickling of a liquid downward through a contact or filtering medium.

Permeability

Definition: The ability of a porous medium such as soil to transmit fluids or gases.

Septage

Definition: The liquid and solid materials pumped from a septic tank during cleaning operations.

Septic Tank

Definition: A buried, watertight tank designed and constructed to receive and partially treat raw wastewater. The tank separates and retains settleable and floatable solids suspended in the wastewater and discharges the settled wastewater for further treatment and dispersal to the environment.

Source: United States Environmental Protection Agency’s Septic System Glossary