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Septic Systems 101

A Quick Lesson For Every Homeowner

A basic septic system has 3 parts: the septic tank, the drain field, and the
soil beneath the drain field.

All water and wastes enter the tank at the inlet baffle. The solids then settle out to the bottom. This is referred to as the sludge layer. Lighter solids like fat, grease and paper, float to the top and create the scum layer. What lies between these two layers is called the effluent. It is a clear, treatable liquid.

Settling is very important to a system's ongoing performance. Washington Code now requires all new tanks to have two like compartments. The effluent crosses over through a center baffle to settle out layers for a second time. Microbes digest and break down much of the waste ~ therefore creating a better treatment.

The effluent then leaves the tank through the outlet baffle and flows down a pipe to the drain field. A normal drain field is comprised of several parallel, perforated 4-inch pipes. A distribution box is needed to ensure that the flow remains equal to all parts of the field. Drain fields are located just below the surface and are usually filled with gravel.

As the effluent seeps out the pipes, it trickles down through the gravel to the soil underneath. Through natural biological processes, the soild purifies the wastewater and allows it to return to the water table and be reused.

Thanks to Clallam County for providing the septic facts found throughout this website.