What does the suction gauge monitor in a centrifugal fire pump system?

• A. Monitors intake pressure to ensure prime.
• B. Measures discharge pressure on the system.
• C. Ambient air temperature near the pump.
• D. Water flow velocity in the suction line.

Answer: (A)

In a centrifugal fire pump, getting water from the source hinges on prime—the pump must be filled and able to pull water in. The suction gauge sits on the suction side and shows the intake pressure at the pump inlet. This tells you whether the pump is primed and whether there’s a healthy suction head. If the reading is too low or shows a strong vacuum, prime may be lost, there could be air leaks, or the suction head isn’t adequate, which can lead to cavitation and reduced flow. The discharge gauge, not the suction gauge, monitors the water pressure on the system’s outlet. Ambient temperature at the pump and water flow velocity in the suction line aren’t what the suction gauge measures. So monitoring intake pressure to ensure prime is exactly what the suction gauge is for.