Why a Sprinkler Head Leaks When the System Is Off: Diaphragm Wear

Slow Leak from a Head After Shutdown

A trickle from the lowest head(s) when the system is off means the zone valve isn’t sealing completely. The rubber diaphragm has worn, allowing water to seep past.

Repair

1. Identify the valve for the leaking zone.
2. Shut off main water, relieve pressure.
3. Remove the valve bonnet, replace the diaphragm (and solenoid O‑ring if needed).
4. Reassemble and test.

Valve rebuild instructions at irrigationtutorials.com.