Septic Systems

More than one of four homes in the Puget Sound area rely on septic systems to treat and dispose of household wastewater. A properly designed, installed and maintained septic system call provide an efficient method of wastewater treatment, adequately treating sewage before it mixes with surface or ground waters. In the last 10 years, most Puget Sound shellfish harvest restrictions have been in rural and semi-rural areas served by septic systems. Failures of these systems are a major contributor to the pollution which forced the restrictions. As a householder, you need to understand how to keep your system working well.

How Your Septic System Works –

Septic systems have two key components – a SEPTIC TANK and a SOIL ABSORTION SYSTEM. The septic tank is a container, usually with two compartments, fabricated from concrete or plastic.

Wastewater from your bathroom, kitchen and laundry room enters the septic tank through your building sewer.

Heavy solid particles settle to the bottom where bacterial action
converts them to a digested sludge.

Settling and breakdown of solids takes time and your tank must be large enough for complete digestion to occur.

The drainfield is the soil absorption system and consists of a distribution box, perforated distribution lines made of plastic or tile, and an area of soil. In the drainfield, disease causing microorganisms and some suspended solids and nutrients are removed as the liquid is absorbed by the soil. If the soil cannot absorb the liquid at the rate at which it enters the septic tank, the plumbing will “back up” or wastewater will bubble to the surface in the drainfield.

The soil also needs time to filter out these harmful materials from the wastewater. “Suitable soils” do not include sand (which permits wastewater to pass through too fast) or clay (which accepts only small amounts of wastewater). Siting your septic tank is a critical decision regulated by local and state health regulations. Consult your county health department before constructing or remodeling your septic system.