Pump runs but makes a rattling noise, especially at startup.

Safety first: Unplug the pump before opening the strainer or pump housing.

• Inspect basket and impeller: Remove the strainer basket and look for debris. If noise persists, remove the pump housing cover to access the impeller.
• Remove debris: Clear any small stones or hard objects from the impeller vanes.
• Tighten impeller: Ensure the impeller is securely threaded onto the motor shaft (if threaded design). Do not overtighten.
• Replace impeller: If the impeller hub is worn or cracked, replace the impeller.