A diaphragm pump (also known as a Membrane pump) is a positive displacement pump that uses a combination of the Air Diaphragm Pump reciprocating action of a rubber, thermoplastic or teflon diaphragm and suitable valves on either aspect 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. … Both diaphragms that are linked by a shaft through the center section where in fact the air valve is situated.
Though this will depend upon the pump and application, a positive displacement pump, is normally a self-priming pump. … For instance, air managed diaphragm pumps self-prime by creating a pressure differential in the diaphragm 
chamber. This draws in air flow and pulls the liquid in to the suction port.
