Types of Systems


Conventional Systems


Gravity System — Basic or standard system, uses gravity to move effluent through the septic tank and into the drainfield. For more information, see Gravity System.

Pressure Distribution System — Has a pump which distributes effluent throughout the drainfield at the same time. Used in most new systems because it makes better use of the entire drainfield. See Pressure Distribution System for additional information.


Alternative Systems


Aerobic Treatment Unit (ATU) — Uses oxygen to break down solids, producing cleaner wastewater than conventional types. Often used in environmentally sensitive areas where effluent requires more treatment before entering the drainfield. For additional information, see Aerobic Treatment Units (ATUs).

Mound System — Installed when minimal soil is available for treatment, drainfield is raised above ground level. See Mound System for more details.

Sand Filter System — Has a sand filtering system and pump to treat and disburse effluent, used when minimal soil is available for treatment. To find out more, see Sand Filter System .


Proprietary Systems


Glendon® BioFilter — This alternative system consists of different layers of sand and gravel placed in a watertight box. Sewage effluent is pumped into the bottom of the filter and then works its way up through the sand and out into the soil. For additional information, see Glendon BioFilters (WA Dept of Health publication).

AdvanTex Filter — In this system, the effluent is filtered through a bed of engineering textile material that is enclosed in a watertight container. This allows treatment of a large amount of wastewater in a small space and is clean enough for subsurface irrigation.

Drip Irrigation — This is a shallow, pressure-dosed system that equally distributes pretreated waste-water at a slow rate over the entire drain field, preventing saturation of the soil.