The frequency of pumping out will depend primarily on the amount of wastewater and solids that go through the system each day. The frequency also depends on how careful you are about not introducing excess fats, soaps, hygiene items, and other similar garbage down the drains. The more solid waste thrown in the system, the quicker the tank will fill up. If a garbage disposal is used, pumping more often is advised to remove the solids. Heavy flows of water also tend to make the tank fill up more quickly and why water should not be left running indiscriminately in sinks and toilets.