In the flexible impeller pump , sometimes called a flexible vane pump, the rotor is made of an elastomeric material such as rubber. The blades of this “impeller” continuously deflect and straighten as they pass across a cam between the inlet and discharge ports. The flexing of the blades produces a vacuum that causes liquid to flow into the space between the two blades and then moves the liquid through the pump
Advantages of the flexible impeller pump include the fact that it is dry self-priming; can handle liquids with solids, abrasives, or entrained air; and is relatively inexpensive. Disadvantages include the upper limits of flow (about 150 gpm) and pressure (about 60 psi) and the fact that the pump can not run dry longer than a couple of minutes without doing damage to the rubber impeller.