Diagnosing Pump Knocking in an Irrigation System

A knocking noise in a system with a Rain Dial controller, Grundfos pump, and Pope solenoid valves could originate from either the pump or the valves. The system previously ran without noise.

Pump-Related Causes

• Cavitation: Air in the suction line or a restricted intake causes violent bubble collapse.
• Loose Impeller or Spacers: Internal components may have come loose, allowing the impeller to strike the casing.
• Suction Line Issues: A loose suction line or damaged spacers can create banging.

Valve-Related Causes

If the noise comes from the valves, the flow control may need adjustment—typically increasing the flow setting. Inspect each valve's flow control knob and open it further if partially closed.

Because pump knocking can indicate serious damage, a professional inspection is advised if the source isn't immediately clear.