A diaphragm pump, also known as a membrane pump, uses a flexible membrane to draw fluid or air into the pump chamber. The same membrane pushes the fluid out of the pump chamber. A piston is attached to an elastomeric membrane, when the piston is withdrawn flexing the membrane away from the pump chamber, the fluid enters the chamber through the inlet. As the piston is advanced pushing the membrane into the chamber a one way check valve closes the inlet and the fluid leaves the chamber through the outlet. When the piston is withdrawn again, the check valve in the outlet closes and the valve in the inlet opens.
There are many different designs for diaphragm pumps including electric, mechanical and air driven. Diaphragm pumps have good suction, they can handle sludges, slurries and liquids with high viscosity, they can self prime, they can run dry without damage. They can be used for industrial chemicals, waste handling, and also hygienic purposes (artificial heart). Diaphragm pumps have a pulsing flow which may be undesirable in some applications. Manufacturers for laboratory diaphragm pumps include but are not limited to: Welch, Gast, KNF, Labconco, and Brandtech.