What is the primary purpose of a discharge relief valve on a fire pump?

• A. To prevent backflow into the pump intake
• B. To regulate engine RPM
• C. To bypass water back to the intake when the discharge pressure reaches the valve setting
• D. To maintain constant nozzle pressure

Answer: (C)

A discharge relief valve is there to protect the pump and the system from overpressure. When discharge pressure rises to the valve’s set point, the valve opens and bypasses water back to the pump’s intake, lowering the pressure in the discharge line. This lets the pump operate safely without forcing excessive stress on hoses, fittings, or the pump itself, especially during rapid changes in demand or valve closures. It isn’t used to regulate engine RPM—that’s handled by the governor—and it doesn’t guarantee a constant nozzle pressure, which depends on flow and demand; the relief valve simply prevents dangerous overpressurization.