Sprinkler Pipe Grinding/Humming Noise: Water Hammer Fix

Symptom: Noise in Pipes on Zones 3,4,5,7

A "grinding/humming" noise heard inside and outside the house on specific zones, which stops when an outdoor faucet is opened, indicates water hammer caused by high velocity and sudden valve closure.

Immediate Adjustment

On each noisy zone's valve, open the flow control (large knob) fully or slightly more. This reduces pressure drop across the valve and dampens hammer.

If Noise Persists

• Install water hammer arrestors on the mainline near the valve manifold.
• Check for undersized pipe on those zones.
• Ensure valves close slowly (some have adjustable closing speed).

Reference

irrigationtutorials.com/waterhammer.htm explains causes and solutions in detail.