Spa makes loud banging or knocking noises when pumps start or stop

Safety: Turn OFF power at the GFCI breaker before inspecting plumbing.

• Bleed air from system: Loosen pump and heater unions slightly to release trapped air, then retighten.
• Secure plumbing: Inspect PVC pipes and manifolds in the equipment bay. Add or tighten clamps and supports to prevent movement when pumps start/stop.
• Inspect check valves: Locate any check valves and ensure they are installed correctly and not slamming excessively. Replace worn or noisy check valves.
• Check pump mounts: Verify that pumps are securely bolted to their bases and that rubber isolation mounts are intact.