A diaphragm pump (also referred to as a Membrane pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber, thermoplastic or teflon diaphragm and suitable valves on either part 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 fluid through the pump. … The two diaphragms that are connected by a shaft through the center section where in fact the air valve is located.

Though it depends upon the pump and application, a positive displacement pump, is generally a Air Diaphragm Pump self-priming pump. … For instance, air managed diaphragm pumps self-primary by creating a pressure differential in the diaphragm chamber. This allures air and pulls the fluid into the suction port.