Septic Tank Pumping
Septic systems are designed so that only the effluent is discharged from the tank into the drain field (also called the leach field). This is simply a set of pipes with holes drilled into them that release the effluent below ground (but above the water table). The effluent is degraded enough to be well-filtered by good soil. There's plenty of organic material left in the effluent, though, which acts as fertilizer. This is why the drain field usually boasts the healthiest segment of the yard above it.
Simple as their design may be, septic systems require the homeowner to monitor them before problems arise. Usually, once a problem becomes obvious, it's too late for any simple solution. Fixing big septic problems often requires thousands of dollars worth of parts and labor. Fortunately, a little maintenance can go a long way in avoiding problems. While pumping frequency is a function of use. Every year for heavy use, every three to five years for moderate useage.