A diaphragm pump (also called a Membrane pump) is a Air Diaphragm Pump positive displacement pump that runs on the mixture of the reciprocating actions of a rubber, thermoplastic or teflon diaphragm and suitable valves on either side of the diaphragm

A double diaphragm is a positive displacement pump which utilises two flexible diaphragms that reciprocate backwards and forwards, creating a short-term chamber, which both draws in and expels liquid through the pump. … Both diaphragms that are connected by a shaft through the center section where the air valve is located.

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 into the suction port.