answer: A diaphragm pump (also known as a Membrane pump, Air Operated Double Diaphragm Pump (AODD) or Pneumatic Diaphragm Pump) is a positive displacement pump that uses a combination of the reciprocating action of a rubber , thermoplastic or teflon diaphragm and suitable valves either side of the diaphragm ( check valve , butterfly valves, flap valves, or any other form of shut-off valves) to pump a fluid .