How can you prevent water hammer when opening discharge valves?

• A. Open valves gradually, maintain consistent speed, and avoid sudden pressure changes.
• B. Open valves quickly to establish flow quickly.
• C. Increase throttle before opening any valve.
• D. Open discharge lines in rapid succession with no sequencing.

Answer: (D)

Water hammer happens when a rapid change in flow velocity creates a sudden pressure surge in the piping. Opening discharge valves too quickly lets the water slam into the valve and downstream piping, causing shock waves that can damage equipment and joints.

Prevent it by easing valve operation: open valves gradually and smoothly, so the flow ramps up rather than jumps to full speed. Keep the pump running at a steady speed to maintain a gentle, continuous increase in flow, avoiding abrupt throttle changes. If multiple discharge lines are involved, open them in a controlled sequence rather than all at once, so each line adds flow without creating a large simultaneous surge.

In short, slow, controlled valve openings and coordinated sequencing minimize velocity spikes and protect the system from water hammer.