A mechanism installed inside or directly adjacent to a pump housing to control the direction and volume of fluid movement. These include suction and discharge valves in reciprocating pumps that open and close with each stroke to maintain one-way flow. Proper seating and timing of these components prevent backflow, cavitation, and loss of prime during operation.
The discharge pump valve is sticking open on the upstroke, which is why we're losing pressure in the main line.
Related terms
Poppet valve
A directional valve consisting of a flat disk on a stem that lifts away from its seat to permit flow.
Snifting valve
An automatic relief valve used to vent trapped air from a steam cylinder or pump.
Cylinder
The tubular chamber in which a piston travels to compress a fluid or convert fluid pressure into mechanical work.