How Septic Systems Work

Septic-SystemA typical septic system has four main components: a pipe from the house, a septic tank, a drainfield and the soil. Microbes in the soil digest or remove most of the contaminants from wastewater before it reaches ground water.

Pipe from the house: All of your household wastewater, from sinks, commodes, dishwashers, and washing machines, exits your house through a pipe to the septic tank.

Septic tank: The septic tank is a buried, watertight container, typically made of concrete. It holds the wastewater long enough to allow solids to settle out (forming sludge) and oil and grease to float to the surface (as scum). It also allows the partial decomposition of the solid materials. A T-shaped outlet is installed to prevent the sludge and scum from leaving the tank and travelling into the drainfield area.

Effluent filters also help to keep solids from entering the drainfield. These are typically found on newer systems, which also often have risers with lids at the ground surface for easy location, inspection, and pumping of the tank. EcoSeptix Alliance offers retrofits of risers and filters on older systems as a tool to improve system maintenance, performance, and longevity.

Drainfield: Wastewater exits the septic tank and is discharged into the drainfield for further treatment by the soil. The partially treated wastewater is pushed along into the drainfield for further treatment every time new wastewater enters the tank.

If the drainfield is overloaded with too much liquid, it will flood, causing effluent to flow to ground surface or create backups in plumbing fixtures. The Virginia Department of Health requires that new system designs include a reserve drainfield area in the event the primary drainfield fails.

Soil: Septic tank wastewater flows to the drainfield, where it percolates into the soil, which provides final treatment by removing harmful bacteria, viruses, and nutrients. Suitable soil is necessary for successful wastewater treatment.