What is the recommended action after priming is complete?

• A. Open discharge lines immediately
• B. Keep priming valve open and monitor
• C. Close priming valve, then open discharge lines gradually
• D. Stop the engine and drain the priming system

Answer: (C)

After priming is complete, the goal is to seal the priming circuit and transition to normal pumping without letting air back in and without causing a surge. Closing the priming valve isolates the primed water from the prime line, preserving the prime in the pump and suction. Then gradually opening the discharge lines allows pressure to rise smoothly, preventing water hammer and minimizing the chance of losing prime as the system comes up to flow. Opening discharge lines immediately can disturb the prime and cause a drop in suction pressure. Keeping the priming valve open keeps the system ready but doesn’t provide the controlled transition needed after a successful prime, and stopping the engine and draining the priming system wastes the prime and requires re-priming.