Commonly called piston pumps, these are often used in high-pressure applications, such as hydrostatic testing of pipelines, tanks, and valves. Flow and outlet liquid pressure can be controlled by varying the air pressure. To calculate discharge liquid pressure, multiply the air pressure by the ratio shown in the table. Pumps are self-priming, which means they create a suction force to draw liquid upward to fill the pump chamber.

Note: Pumps must be filled with liquid before use. They need a constant flow of liquid and cannot run dry.