Some material in this bulletin was adapted from Bulletin EB1671 prepared by Cooperative Extension, Washington State University. Households that are not served by public sewers usually depend on septic systems to treat and dispose of wastewater. This file contains information that will help you manage your septic system. It also provides a place for you to record and store vital information about your system. It should be filed with other documents about your home and property.
Wastes flow from the house into the septic tank.
Here, most solids are separated to the bottom and are partially decomposed by bacteria to form sludge. Some solids float and form a scum mat on top of the water. The liquid effluent from the septic tank, carrying disease-causing organisms and liquid waste products, is discharged into the soil absorption field. Here the water is further purified by filtration and decomposition by microorganisms in the soil. The semi-purified wastewater then percolates to the groundwater system.