Septic System Terminology and Definitions

Absorption Field: A subsurface leaching area within the soil that receives the liquid effluent from the distribution laterals and distributes it over a specified area where it is allowed to seep into the soil.

Active System: A septic system that requires external energy and mechanical components to function.

Aeration Chamber: A volumetric container made of concrete, fiberglass, steel or plastic. The Aeration Chamber may be fabricated integrally with a septic tank and is designed to house equipment which introduces oxygen (air) into the effluent.

Aerobic Bacteria: Odorless, highly efficient strains of sewage digesting bacteria that live only in the presence of oxygen.
Anaerobic Bacteria: Less efficient strains of sewage digesting bacteria that live only in the absence of oxygen.

Biomat: Black, slimy growth and by-product of anaerobic bacteria that grows at the interface of the distribution component and the surrounding soil. If neglected, the biomat becomes impermeable and can cause septic system backups and failure.

Black Water: Influent containing human waste.

Cesspool (or Cesspit): A pit dug into the ground with the walls loosely lined by stone or brick to allow liquid effluent to seep out of the cesspool into the ground while holding the solids in the pit.

Clear Zone: The middle layer of gray or brownish, murky liquid in a septic tank that is mostly comprised of water with small microscopic matter in suspension.

Distribution Box: A hollow cylindrical or cubical structure constructed of concrete, fiberglass, plastic or steel. The Distribution Box is located underground between the septic tank outlet and the distribution field.

Distribution Cell: A narrow trench that contains a perforated piping system embedded and covered in washed gravel in such a manner that effluent can flow into it from a distribution component and be uniformly dispersed into the ground.

Distribution Component: Drainfield, seepage pit or mound designed to distribute effluent into the ground.

Distribution Field: Another name for absorption field.

Distribution Laterals: A distribution component extending from the main distribution pipe to the edges of the distribution field designed to uniformly distribute effluent into the ground.

Drainfield: Another name for absorption field.

Dry Well: A hollow, porous chamber located underground, constructed using the ground for walls or loosely lined with concrete block, cinder block, or bricks in such a manner that effluent can flow into it from a septic tank and be uniformly dispersed into the surrounding ground.

Effluent: Wastewater which flows out of a septic tank.

Effluent Baffle: A t-shaped, tubular device open at the top and bottom having the third leg attached horizontally at the outlet of a septic tank. Typically made of pvc pipe or fiberglass designed to prevent surging and discourage the flow of solids out of the septic tank into the distribution components.

Effluent Filter: A housing and cartridge typically made of plastic located at the outlet of a septic tank containing small openings or bristles that allow liquids to pass through but block the flow of solids out of the septic tank into the distribution components.

Effluent Pump: A pump used to transfer liquid effluent from a pumping chamber to a distribution component when the effluent cannot flow by gravity.

Gray Water: Wastewater which does not contain human waste. Gray water is created from the use of laundry facilities, dishwashers, bathing, or other similar household activities.

Influent: Raw, untreated sewage and wastewater which flows into a septic tank.

Leach field: Another name for a distribution field.

Passive System: A septic system that does not require external energy and mechanical components to function.

Seepage Pit: Another name for dry well.

Septic: Putrefactive, rotten, to make rotten. Lacking oxygen.

Septic Tank: A tank made of concrete, fiberglass, plastic or steel used in a septic system in which accepts influent and is designed to separate and hold the solid matter of continuously flowing sewage. The tank also holds bacteria required for the digestion of the solids.

Septic Tank Riser: An extension of the septic tank used to raise the tank cover to ground level or higher for easy septic tank maintenance. Septic risers are easy to install and are designed to work with a wide variety septic tank configurations.

Settling Chamber: A volumetric container made of concrete, fiberglass, steel or plastic, that may be fabricated integrally with a septic tank. The Settling Chamber is designed to substantially slow the flow rate of effluent to provide sufficient time for solids to precipitate out of the liquid effluent.

Sludge Layer: The bottom layer of matter in a septic tank that is heavier than water and comprised mostly of solids.

System Failure: A condition when a distribution field becomes saturated and foul-smelling effluent appears on the ground above the distribution component creating a health and environmental hazard.

Treatment Chamber: Large volume container made of concrete, fiberglass, steel or plastic designed to hold sewage so that the sewage can be biochemically processed.

Vent Pipe: A vertical pipe made of plastic, steel, clay, or cast iron, that is connected to a component of a septic system that allows displaced air to flow to the atmosphere.

Vented Cover: A cover made of concrete, fiberglass, steel or plastic that has an integral vent pipe or opening.