A diaphragm pump (also referred to as a Membrane pump) is a positive displacement pump that uses a combination of the reciprocating actions of a rubber, thermoplastic or teflon diaphragm and suitable valves on either side of the diaphragm
A dual diaphragm is a positive displacement pump which utilises two flexible diaphragms that reciprocate back and forth, creating a short-term chamber, which both allures and expels fluid through the pump. … Both diaphragms that are linked by a shaft through the center section 
where the air valve is located.
Though this will depend upon the pump and application, a positive displacement pump, is generally a self-priming pump. … For instance, air Air Diaphragm Pump managed diaphragm pumps self-prime by creating a pressure differential in the diaphragm chamber. This allures air and pulls the fluid into the suction port.