There are three major types of pool filtering system: cartridge, sand, and diatomaceous earth (DE). Sand and DE filters use a multiport valve primarily to help clean or backflush the filter media. Cartridge filters do not have multiport valves. These filters are cleaned by removing the cartridge and spraying it with a garden hose. A typical multiport valve has 7 settings: filter, backwash, rinse, waste, closed, recirculate, and winter. This guide explains the function of these setting and shows how they circulate water in a typical sand filter. The operation of a DE multiport valve is very similar.