If you live in a rural area or have vacation property in the middle of nowhere, you no doubt are familiar with the form and function of a septic system. Or, you might be considering the construction of a home or weekend getaway where a septic system will be required and are curious to know how such a system works.

In brief, a septic system is your very own onsite sewage treatment facility. It is used primarily where access to a municipal sewer system is neither available nor economically practical. It is out of sight and is odorless (when properly maintained).

A septic system consists of a tank buried below ground and a series of drain lines - called a leach field - that cleanse and purify wastewater. Thus, instead of being piped to a municipal sewage treatment plant, the sewage stays close to home. Although in theory the water that makes its way through the entire system is said to be pure enough for human consumption, the leach field must be located well away from a well.

The first component of a septic system is a drainpipe that carries the raw sewage from the home into the septic tank - the second part of the system. The tank, which can be constructed of various materials (wood, concrete, steel, fiberglass), is watertight and virtually airtight. It is a settling tank that collects and stores sewage solids. By design, the sewage remains in the tank long enough for beneficial anaerobic bacteria to break down the solids. Keep in mind that 99.9 percent of most residential sewage is water, while only .1 percent is solids.

Incoming sewage displaces an equal amount of liquid, which is discharged via gravity through an outlet that is positioned slightly lower in the tank than the inlet. This liquid, called effluent, is discharged into a network of drainage pipes and then into the surrounding soil. This part of the septic system is referred to as the "leach field." This action filters the effluent as aerobic bacteria further break it down to create nutrients and chemicals that are beneficial to plant life. However, using too much water can upset the delicate biological balance within the tank, thus defeating its ability to work wonders. Moreover, discharging more water into the system than it can handle can cause it to back up - not a desirable occurrence.

A septic system is reasonably maintenance-free. A well-constructed, properly maintained tank could last indefinitely. However, the leach field will most likely require some treatment or perhaps replacement after about 15 to 20 years of service.

The following precautions and routine maintenance tasks will keep the system working efficiently for many years:

-Be mindful about what you and your family put into your septic system. It doesn't take much to upset the delicate biological balance within the tank, thus defeating its ability to work wonders. Watching everything that is introduced to the system, adding bacteria to dilute the amount of sludge and regular pumping are ways to extend the life of a septic system.

-Normal amounts of household detergents, bleaches, drain cleaners and other household chemicals can be used and won't stop the bacterial action in the septic tank. But don't use excessive amounts of any household chemicals. Do not dump cleaning water for latex paint brushes and cans into the house sewer.

-Don't deposit coffee grounds, cooking fats, wet-strength towels, disposable diapers, facial tissues, cigarette butts, and other non-decomposable materials into the house sewer. These materials won't decompose and will fill the septic tank and plug the system.

-Avoid dumping grease down the drain. It might plug sewer pipes or build up in the septic tank and plug the inlet. Keep a separate container for waste grease and throw it out with the garbage.

-Use a high quality toilet tissue that breaks up easily when wet. One way to find out is to put a handful of toilet tissue in a fruit jar half full of water. Shake the jar and if the tissue breaks up easily, the product is suitable for the septic tank.

-Clean your septic tank every one to three years. A septic tank in a northern climate will need to have the solids removed more often than a tank further south. This is primarily because of cooler temperatures, which inhibit bacterial action and provide less decomposition of the sewage solids. How often depends on the size of the tank and how many solids go into it.

Following a few simple rules like not using too much water and not depositing materials in the septic tank that bacteria can't decompose should help to make a septic system trouble-free for many years. But don't forget the septic tank does need to be cleaned out when too many solids build up.