A diaphragm pump is a pump that uses a flexible membrane to move fluid through a chamber. In the pool industry, these pumps are often used as components in an automated chemical feeding system, for introducing measured doses of chemicals like chlorine into the pool.
Because diaphragm pumps transport chemicals through a sealed casing, they can be used to move hazardous chemicals into the pool's circulation system.
Within the diaphragm pump's main casing, the diaphragm's movement is controlled by a rotating non-circular part, such as a solenoid or a cam. When the diaphragm moves outward, this creates suction that moves liquid into the central chamber. As the chamber fills up with fluid, the pressure inside the chamber is equalized, causing a spring-loaded check valve at the entrance of the chamber to close. This pressure also causes the diaphragm to move inward, forcing the fluid out through the exit check valve and into the pool's circulation system. This cycle is repeated once for each injection of a chemical dose.
Because the balance of fluid pressure must be maintained for the system's check valves to function properly, it is crucial to check that all valves are movable, and that fluid is flowing freely through the pumps, on a regular basis. Some recommend flushing the entire system as often as once per week.