How Septic Systems Work

When properly cared for, a septic system makes an excellent on-site wastewater treatment centre, located conveniently in your back yard. It is an arrangement of tanks, pipes, and surrounding soil which work together to treat household wastewater.

The treatment process begins when household wastewater enters the septic tank through an inlet tee. The septic tank is a buried, watertight container typically made of concrete, fiberglass or polyethylene and consists of two chambers. As the wastewater flows into the septic tank, the heavy solids settle to the bottom of the tank, forming a sludge layer. Lighter materials such as fats, oils, or grease float to the top forming a scum layer, leaving partially treated wastewater in the middle. Baffles and screens within the tank keep the scum from escaping to the leaching bed. The sludge and scum layers are acted upon by naturally occurring bacteria which work in the anaerobic (oxygen-poor) conditions of the tank and slowly decompose the solid waste. They cannot decompose all the solid waste, therefore, it is important to have your tank pumped out every three to five years. Newer tanks generally have risers with lids at the ground surface to allow easy location, inspection and pumping of the tank.

Next, the partially treated wastewater flows out of the tank by an outlet tee, where it will begin the next step of treatment in the leaching bed. The leaching bed consists of a series of perforated drain pipes. As the wastewater enters the pipes it slowly percolates down from the pipes and into the soil. The soil organisms and the soil itself act as filters by removing nutrients, toxins, bacteria, metals and organisms from the wastewater. As the wastewater continues to move down through the soil, pollutants are removed and eventually the treated water returns to the groundwater system.

Even though your septic system is out of sight, it plays an important role in treating household wastewater. So make sure you maintain your system by getting it inspected and pumped out every three to five years by a professional!