Often overlooked or neglected is the fact that a septic tank system should be checked regularly to prevent problems. Remember, the septic tank traps the solids in the wastewater and therefore it occasionally needs to be pumped out. A properly designed system has a septic tank large enough to accumulate solids for several years. If the level of solids fills too much of the space in the tank, the wastewater does not have enough time to settle properly and too many solid particles flow into the drainfield. If the tank is not periodically pumped out, this will eventually cause the drainfield to clog to the point where a new field will be needed.

This table provides, on average, how often a septic tank should be pumped out given the size of the tank and the number of persons living in the household. These figures assume there is no garbage disposal unit in use. The use of a garbage disposal will increase the amount of solids in the holding tank by as much as 50 percent, and is not recommended to be used on a septic tank system.