Sprinkler Zone Won't Shut Off? Troubleshoot a Stuck Valve

You've moved into a 10-year-old home with a four-station sprinkler system. Everything worked fine until two days ago — station 3 started leaking from six heads, and the valve box has water running continuously. You've replaced all solenoids, but the zone still won't shut off. Now you've shut off the main irrigation supply to stop the waste.

Start with the Flow Control

Every irrigation valve has a flow control knob on top — usually the larger of two knobs. This regulates how far the diaphragm opens. If it's wide open, the valve may not close fully, especially with lower pressure.

Try this adjustment sequence:

1. Turn the flow control clockwise until fully closed. Count the turns.
2. Open it counterclockwise exactly half that number of turns.
3. Test the zone manually from the controller.

If That Fails: Clean the Valve

Debris in the valve body can prevent the diaphragm from sealing. Shut off the water, disassemble the valve carefully (note the spring and diaphragm orientation), and flush out any sand, grit, or mineral buildup. Inspect the diaphragm for tears or warping — replace if damaged. Reassemble with waterproof wire connectors on the solenoid leads.

When to Call a Pro

If adjusting and cleaning don't work, the valve body itself may be cracked or the seat eroded. At that point, replacing the entire valve is faster and more reliable than continued troubleshooting.