How a Septic System Works

Septic Tank

The septic tank is the primary underground holding vessel for all wastewater leaving a home or building. It separates solid waste from liquid effluent through settling and natural bacterial action, holding solids while allowing clarified liquid to flow toward the drain field. It is the first and most fundamental component of any on-site sewage system.

Drain Field

Also called: leach field, absorption field, drainfield

The drain field - also called a leach field or absorption field - is the section of the septic system that receives clarified liquid effluent from the septic tank and disperses it into the surrounding soil for final treatment and disposal. It is typically a network of perforated pipes laid in gravel-filled trenches. The biological and physical processes in the soil remove remaining pathogens and nutrients before the treated water re-enters the groundwater.

Distribution Box

Also called: d-box, diversion box

A distribution box - often called a D-box - is a small concrete or plastic chamber that sits between the septic tank and the drain field. It receives clarified effluent from the tank and divides that flow evenly among two or more drain field trenches. Proper distribution ensures that no single trench bears a disproportionate share of the hydraulic load, which would cause that trench to fail prematurely while the others remain underused.

Effluent Filter

Also called: outlet filter, septic filter

An effluent filter - also called an outlet filter - is a cartridge installed inside the septic tank at the outlet baffle. Its job is to prevent small solids, hair, and floating scum particles from leaving the tank and reaching the drain field. Effluent filters have become standard on newer systems and are increasingly recommended as a retrofit on older ones because protecting the drain field from solids can significantly extend its useful life.

Pump Chamber

Also called: dosing chamber, pump tank, lift station tank

A pump chamber - also called a dosing chamber or pump tank - is a separate watertight compartment that receives clarified effluent from the septic tank and uses a submersible pump to deliver it to the drain field on a controlled schedule. It is used when gravity flow to the drain field is not possible or when controlled dosing is required by the system design or county regulations. The pump chamber typically houses the pump, the float switches that control pump operation, and the alarm float.

Septic Alarm

Also called: pump alarm, control panel alarm, high-water alarm

A septic alarm - also called a pump alarm or high-water alarm - is an audible or visual alert connected to float sensors in the pump chamber. It activates when the liquid level rises above the normal operating range, signaling that the pump may not be running, that water use has temporarily exceeded the pump's capacity, or that a float switch has failed. The alarm exists to give a warning window before the chamber reaches a critical level.

Risers and Access Lids

Also called: septic covers, cleanout lids, access ports

Risers are vertical extensions - typically made of plastic or concrete - that connect the underground access openings of a septic tank or distribution box to ground level or near-surface level. Access lids seal the top of the riser, preventing odor release, surface water intrusion, and accidental entry. Together, risers and lids can allow General Septic to discuss access without excavating for every request.