What is the purpose of the intake relief valve on some fire pump setups?

• A. To regulate discharge flow to fixed rate
• B. To prevent suction line cavitation by venting excess pressure or air on the suction side and maintaining prime
• C. To vent exhaust from engine
• D. To drain water when shutting down

Answer: (B)

The key idea is keeping the suction side primed by venting air and preventing suction-side pressure issues. An intake relief valve opens to vent any trapped air or abnormal pressure on the suction line to the atmosphere. By releasing that air, the suction path can fill with water and stay primed, which prevents cavitation and loss of prime as the pump runs. It’s not about controlling discharge flow, venting engine exhaust, or draining water when shutting down—those functions use different components.