What are the signs that a pump has successfully primed?

• A. High noise and vibration with pressure spikes.
• B. No suction gauge movement and no water at priming device.
• C. A stable suction gauge reading within expected range and visible water at priming device, then steady discharge pressure.
• D. Uneven discharge pressure and erratic suction gauge.

Answer: (C)

Priming a fire pump means filling the pump and suction line with water to purge air so the pump can develop flow. When the prime is successful, the suction side should show a stable reading on the suction gauge within the expected range and you should be able to see water at the priming device, confirming water has reached the pump inlet. Once those signs are present, the pump will begin delivering water and the discharge pressure should rise to a steady, consistent level rather than fluctuating.

If the suction gauge isn’t moving or you don’t see water at the priming device, the prime hasn’t taken, meaning air is still in the system. If the discharge pressure is uneven or the suction gauge is erratic, the prime is unstable and not fully established.