Hayward PowerFlo pump produces a loud thump or bang at startup or shutdown.

Safety first: Turn off the pump before adjusting valves.

• Open valves slowly: When starting the PowerFlo, open return valves gradually to reduce sudden pressure changes.
• Inspect check valves: Check any discharge-side check valves for loose or slamming flappers. Replace with spring-loaded or quieter designs if needed.
• Bleed air: Use air relief valves on the filter or high points in the plumbing to remove trapped air.
• Consider flow reduction: If plumbing is undersized, consider throttling slightly with a valve (within safe limits) or upgrading plumbing to reduce water hammer.