A diaphragm pump (also referred to as a Air Diaphragm Pump Membrane pump) is a positive displacement pump that uses a mixture of the reciprocating actions of a rubber, thermoplastic or teflon diaphragm and suitable valves on either aspect of the diaphragm

A dual diaphragm is a positive displacement pump which utilises two flexible diaphragms that reciprocate back and forth, creating a temporary chamber, which both draws in and expels fluid through the pump. … The two diaphragms that are connected by a shaft through the centre section where the air valve is situated.

Though it depends upon the pump and application, a positive displacement pump, is generally a self-priming pump. … For instance, air operated diaphragm pumps self-prime by creating a pressure differential in the diaphragm chamber. This draws in surroundings and pulls the fluid in to the suction port.