What is the function of the pressure-relief valve on a pump?

• A. To increase pumping efficiency by speeding water through the pump.
• B. To protect the pump and lines by relieving excess discharge pressure back to the intake when set pressure is exceeded.
• C. To measure discharge flow rate.
• D. To regulate engine temperature.

Answer: (B)

The pressure-relief valve serves to protect the pump and the hoses by venting excess discharge pressure back to the intake when the set pressure is exceeded. If discharge pressure climbs above the valve’s limit—due to a blocked hose, closed valve, or other restriction—the valve opens and returns water to the pump suction, preventing overpressure that could damage the pump, fittings, or lines. This is a safety and protection function, not a means to increase efficiency, measure flow, or regulate engine temperature.