Diaphragm pumps are a positive displacement pump, that are most commonly used for transfer of chemicals and/or viscous products. The diaphragm works on air displacement principle, with the diaphragm/s (membrane) being mechanically pushed and pulled in and out of the fluid (pumping) chamber. When the diaphragm is collapsed the air is forced out of the diaphragm chamber and when the diaphragm is extended the pumped fluid is drawn (sucked) up into the fluid chamber through the suction line. The fluid is then expelled from the fluid chamber as the diaphragm is again collapsed. In order to control the suction and discharge, the inlet and outlet ports/manifolds have a one-way valve. These are commonly ball and seat, flap or duckbill style one-way valves. Diaphragm pumps are available in air-operated, electric, and petrol or diesel engine driven variants.