There are at least eight methods for priming pumps; some of them as a simple as a constant flooding from the source to others as complex as an automatic primer or vacuum pump. These methods are: the flooded suction in which the water flows into the casing by gravity or pressure on the intake; priming with foot valves; priming from an outside supply; priming by a separate hand or manually controlled priming pump; priming by bypassing the discharge check valve; priming by ejector; priming by automatic primer; and priming by manually controlled dry vacuum pumps and by automatic control. The choice of methods usually will depend on the type of installation required, the liquid being handled and the service involved.