Septics 101

How Your Septic System Works

Septic Tank

1. Wastewater from your house flows into the septic tank.

2. The tank provides a holding area in which natural biological processes break down the waste. This allows solids to settle out. Heavier solids sink to the bottom forming what is called the “sludge layer”. The lighter solids such as: grease, oils, fats etc.. rise to the top and form the “scum” layer. The center of the tank which is relatively clear liquid is called “effluent”.

3. Baffles within the tank provide two functions: (A) Inlet Baffle – forces wastewater to slow, and allow the waste entering the tank to break up. (B) Outlet Baffle – is a vital part of the tank, since it prevents floating material from entering the drainfield.


A typical drainfield consists of a series of trenches approx. 2’ wide 18″ deep. Perforated pipes extend the length of each trench. Gravel surrounds the pipe. Water from the septic tank enters the pipe and trickles through the gravel bed, micro organisms in the soil break down the waste. Approximately 30% of this liquid is returned to the atmosphere through evaporation. Keep in mind all systems do vary by design.

At an average of 70 gal. per day, per person of wastewater a family of 4 can use 102200 gallons of water in a year.

Clogging commonly occurs when solids, which settle to the bottom of the tank are not broken down by bacteria. When these solids accumulate they are eventually carried into the drainfield causing clogs in the septic fields. The accumulated solids are called “sludge”. Sludge material does not decompose and therefore will cause your system to require servicing. Sludge accumulation is approximately 80 gallons per person per year, this is equal to 320 gallons per year for a family of four.