Septic Tanks – How They Work

DEAR TIM: I recently purchased a home with a septic tank. Prior to this, all of my houses had public sewers. How in the world do these things work? Should I be concerned with what I put down my drains? What about maintenance, is it required? Bea S., Sugartown, PA

DEAR BEA: Don't worry about a thing, septic tanks are fairly common. Your household as well as approximately 25 million others in the USA rely on these simple, yet highly efficient systems to treat household wastewater. Septic systems, when designed, installed, and maintained properly do a fantastic job of protecting your family's health and that of the environment.

A typical household septic system consists of two major components: the septic tank and the drainfield. Wastewater from your house travels, in most cases, by gravity to the septic tank. The tank's main purpose is to detain the wastewater for 1 - 2 days. It uses this time to separate solids, greases, oils, and floating objects from the wastewater. Bacteria within the tank starts to attack and break down the waste immediately.

Although the bacteria does a good job, it can't eat everything. Septic tanks develop a layered look. Scum floats on the top, partially treated wastewater is in the middle, and sludge settles at the bottom.

After its 1 - 2 day stay, the partially treated wastewater leaves the tank. If everything is working right, virtually all of the solids have settled out of the water. The wastewater now heads for the drain field. This area is comprised of a series of interconnected pipes that lie in sand or gravel filled trenches. The pipes are perforated. The wastewater exits the perforations and enters the soil. The soil acts as a biological filter. Oxygen and organisms in the soil combine to break down any remaining toxins, bacteria, or viruses in the wastewater.

Septic tanks must be sized in accordance with the number of people in the household. Tanks with too little capacity allow the wastewater to enter the drain field too quickly. Solid particles that were supposed to settle into the tank are inadvertently carried into the drain field. These tiny solid particles can clog the sand, gravel and soil filters in the drain field. If this happens, your septic tank can backup and/or the drain field can become flooded with untreated wastewater. Both of these situations are unsanitary and pose serious health risks to you and the environment.

Click below to view Tim's video on the care of Septic Systems.

You can extend the life of your entire septic system by watching what you put into your drains and toilet. Minimize the introduction of solid particles and scum forming compounds. This means no food scraps, coffee grinds, sand, gravel, greases, oils, washing machine lint, etc. Beware of chemicals or solvents that will kill the helpful bacteria in your tank. Do not put pesticides, paints (even latex!), organic chemicals, paint thinner, etc. into your drains. Finally, have your septic system inspected annually and pumped clean on a regular basis. Remember, the sludge and scum must not be allowed to accumulate. If they enter the drain field, you will have an expensive repair bill.

The beneficial bacteria that break down waste inside the septic tank can be stimulated if they get a dose of oxygen every week or so. The oxygen enhances their growth and more bacteria simply means more rapid breakdown of waste particles. One of the best ways to accomplish this is to pour 4 ounces of powdered opens in a new windowoxygen bleach into a toilet and flush it immediately. Do this two times a week and your septic system will silently thank you.

Author's Note: We've received other questions with similar problems or questions. Here's one from Howard Stein of Oklahoma City, OK, regarding his home septic system.

"We have ten inches of snow and the temperature is near zero Fahrenheit. It will stay like this for several days.  Is it safe to use our washing machine (doing regular laundry) in this frigid weather since we have a septic tank and fear that the "arms" cannot properly dispose of large volumes of water into the ground?  Many thanks for your help."

Howard, typically in most septic systems, the tank and drainage fields are located well below the frost line.