Septic tanks and leaching fields are subjects many people would prefer not to think about! However, some basic knowledge of how these systems work will keep them working right, and help to prevent a costly repair job, or septic system replacement. There are two main parts of a standard septic system: the septic tank and the leaching field.
The Septic Tank
The septic tank is usually made of concrete, but with older houses may be stone, brick, or steel. It is large (typically 750-1500 gallons) which allows space for the sewage to become still, so that solids (called sludge) will settle out to the bottom. Bacteria and other microbes in the tank then go to work to break down the solids. The liquid material at the top, called effluent, flows out into the leaching pipes. Baffles in the tank also help to ensure that only liquid, without solids, passes into the leaching pipes.
The Leaching Field
In modern systems the leaching field typically consists of perforated plastic pipes in stone trenches, under the surface of the yard. There are many other configurations of leaching fields that have been used. The leaching field should provide plenty of surface area for the effluent to be absorbed by the soil, where soil bacteria can process it and destroy harmful bacteria and viruses, which are found in raw sewage. In a properly functioning septic system, safe, potable water is returned to the ground water beneath the property. Older leaching systems are often simple, and may be significantly undersized by modern standards. A properly performed septic inspection will identify what type of system is there, whether it is working properly, and if repairs or even complete replacement are necessary.
What can cause a septic system to fail?
There are several causes of problems with septic systems. The most common are:
- Overloading the system with too much flow
- Putting things down the drain which are harmful to the bacteria
- Failing to have the tank pumped periodically to remove built-up solids.
To keep your system working optimally, avoid excessive flow of water to the system all at once. For example, try to space out your loads of laundry, rather than doing it all in one day. Also, avoid putting large amounts of bleach or other chemicals down the drain which may kill the bacteria which are needed to process the solids in the tank. Solvents like paint thinner should never go down the drain. The best maintenance for a septic system is to have it pumped at least once every 3-4 years, or more often, depending on the size of the tank and the number of people in the household. When your tank is pumped, ask the septic contractor how often pumping is recommended for your system. Pumping is quite inexpensive, compared to the cost of leaching field replacement. When sludge builds up, solids begin to enter the leaching pipes and plug the stone and soil around the pipes, eventually causing system failure.
The Septic Inspection
If a septic system is present, it should be inspected by a qualified septic contractor, using a video camera system, before you purchase the house. Note that the contract you sign with the seller often will state that the seller pays the fee for pumping, while you are responsible for the inspection fee and any additional labor that may be required to dig up components of the system. Ask your agent, or the attorney who has drawn up your real estate purchase contract.
In a typical inspection the septic inspector will observe the interior of the tank, to see if fluid levels are, or have ever been, too high (which may indicate a backup in the leaching field). A “snake” with a video camera is used to go out from the tank to identify the components of the leaching field, and to determine if all effluent has been properly absorbed. It may be necessary to dig up a “distribution box” or other component of the leaching field to gain access for a complete inspection. A written report details the findings of the inspection, noting any concerns, repairs, or modifications recommended. You are encouraged to be present at the septic inspection, so that all of your questions may be answered.