About Septic Systems

Why do you need a septic system?

Simple. To help keep our water clean by treating the wasterwater we create.

The University of Minnesota's Onsite Sewage Treatment Program has a great summary of what septic systems do and how they work. Read below:

What do septic systems do?

Septic systems protect human health and the environment by safely recycling wastewater back into the natural environment. Septic systems treat wastewater as well as, or better than, municipal treatment systems at a reasonable cost when properly designed, installed, operated, and maintained.

Federal, state, and local regulation of on-site systems focuses on proper treatment of sewage to protect citizens, communities, and the environment.

How does a septic system work?

In typical on-site treatment systems, all wastewater is co-mingled, treated, and dispersed by one system. There are a few separation systems in which toilet wastes are treated separately from other wastewater.

Common septic systems all have three basic components: plumbing, septic tank, and a soil treatment area. Individual systems may have variations of each of these.


The wastewater side of household plumbing collects used water from fixtures and appliances and delivers it to the treatment system(s).

Septic Tank

The septic tank is a solid watertight tank, or series of tanks, that receives waste water. It separates the solids from the liquids and stores the solids until they are decomposed or removed. The liquid, called effluent, is delivered to the soil treatment system.

Inlet and outlet baffles trap the floating solids in the tank. Inspection pipes allow monitoring of the tank and the manhole facilitates cleaning.

The size of the septic tank is based on the home's potential water use volume and the type of appliances used. In aerobic tank systems, pumps and other mechanisms are necessary to deliver air to the tank.

Soil Treatment Area

The soil treatment part of the typical septic system is a network of perforated pipes or tubes surrounded by small rock and soil. Some designs use large plastic tubes or chambers instead of rock to disperse effluent from the tank into the surrounding soil.

The design of the treatment area (trench, mound, etc.) is based on the soil condition. The soil in the treatment area must not be saturated with water for extended periods of time during the year. Three feet of unsaturated soil below the system is necessary to complete the treatment process.

The size of the soil treatment area needed depends on the volume of water to be treated and the type of soil on the site. For example, a much larger soil area is needed for a large home or a home on clay soil than for a small home or one on sandy soil.

Pumps and a lift station may be components of a system where gravity flow doesn't work. For example, in mounds and drip irrigation systems a pump is required to provide pressurized flow for distribution of effluent.

For more information and to continue reading the article about septic systems from the University of Minnesota, click this link.