Pump makes a rattling or clicking noise, especially at start‑up or shut‑down.

Safety: Isolate power before tightening or inspecting moving parts.

• Tighten hardware: Check and tighten pump base bolts, motor end‑bell screws, and fan cover screws.
• Inspect non‑return valve: Open and inspect any Certikin check valve near the pump. Replace if the flap is loose or damaged.
• Check impeller: Inspect the impeller for small stones or debris that may rattle when spinning.