A
house's septic tank should be pumped to prevent solids from making their
way out of the tank and into the leaching field. A conventional septic system contains two major components–a holding tank and a leaching field. The tank allows anaerobic bacteria to act on the waste and break it down into liquid, sludge and scum. The sludge accumulates on the bottom of the tank. Then the scum floats on top of the liquid and the liquid flows out of the tank to the leaching field. There, it drains through perforated pipes into gravel-filled trenches. The liquid then percolates into the soil.
If the sludge level gets too high, it will be transported by the liquid into the leaching field. The sludge will clog the pipe perforations, the air spaces between the gravel or crushed stone and even the air spaces between the soil particles below. Over time the clogged leaching field will become a soggy, odorous mess with lush grass growing over it. In severe instances, waste can back into the house and flow out plumbing fixtures on the house's lowest level
There are several factors that determine the tank-pumping frequency: the tank's size, the number of people living in the house, whether a garbage disposal is used, and how often laundry is done. Many municipalities recommend a tank be pumped every two to three years. Depending on the factors discussed above, it may need to be done more or less frequently.
A safe approach is to have the tank inspected yearly until it is determined that pumping is required. Once the pumping interval is established, you can follow that until there is a change in water-use patterns that would require the tank to be pumped more or less frequently.
For more information on septic systems, contact the National Small Flows Clearinghouse, West Virginia University, P.O. Box 6064, Morgantown, WV 26506; 800-624-8301. Its Web site is www.nsfc.wvu.edu. The organization publishes a variety of materials, several of which are designed to help homeowners with their septic systems.