What regulates the pump discharge pressure and volume on a low-pressure system?

The correct answer pertains to a pressure switch, which is a device specifically designed to regulate pump discharge pressure and volume within a low-pressure system.

Pressure switches work by monitoring the pressure of the fluid in the system. When the pressure reaches a predetermined level, the switch activates or deactivates the pump, ensuring that the discharge pressure remains within safe and functional limits. This regulation helps maintain efficient operation and prevent potential damage to the system by avoiding over-pressurization and ensuring adequate flow.

While relief valves are important for preventing excess pressure from building up in the system by allowing fluid to escape, their function is reactive rather than regulatory. A plug valve and a manual valve are primarily used for controlling the flow of fluid in a system but do not have the automatic pressure-regulating capabilities provided by a pressure switch. Thus, they simply open or close a passage rather than adjusting the pump's operation based on the discharge pressure.