When the water rises to a certain level, a floating switch completes an electrical circuit and engages the pump. Sumps are usually 2 feet deep and 18 inches in diameter. Check out this video for a simple explanation of how a sump pump works. In the same way, homes have a small pit that’s dug into the floor of the basement to collect water that filters through the loose earth surrounding your foundation.Ī sump pump is a simple device that detects water in the sump and moves it away from the property through a network of pipes. Your car, for instance, has a sump to collect oil. A sump is a low space that collects liquids.