Why Won't My Sprinkler Zone Shut Off?

A zone that won't shut off almost always has a valve that can't seal. The two most common causes are grit in the valve after pipe work, and a bleed screw left open after running the zone by hand. Both are quick to check.

How a zone valve shuts off

Each zone has an electric valve, usually in a box in the yard. Water pressure on one side of a rubber diaphragm holds the valve closed. When the controller sends a signal, the solenoid releases that pressure and the valve opens. When the signal stops, the pressure builds back and the diaphragm seals.

Anything that lets that pressure escape, or keeps the diaphragm from seating, leaves the zone running.

What to check

Work in this order, from easiest to most involved.

1. Rule out the controller. Make sure no program is running and no zone was left on manually. Turn the controller to off for a minute. If the zone stops, the problem is the schedule, not the valve.
2. Look at the bleed screw. Many valves have a small bleed screw on top. It is opened to run a zone by hand. If it was left open, water keeps escaping and the valve stays open. Close it snug by hand.
3. Check the solenoid and the flow-control handle. A loose solenoid can hold the valve open. Snug it by hand. Also check the flow-control handle on top of the valve, since one that is loose, cracked or stuck open can keep the valve from closing fully.
4. Shut off the water to the system. Do this before you open any valve. Use the system shutoff, not just the controller.
5. Open the valve and clean it. Remove the solenoid and bonnet screws. Lift out the diaphragm and spring. Rinse the diaphragm, its seat and the valve body. Look for sand, grit and small stones. Check the diaphragm for tears.
6. Reassemble and test. Seat the diaphragm properly and tighten the screws evenly. Turn the water back on slowly, run the zone from the controller and confirm it shuts off.

Grit after a mainline repair

When a mainline is cut open and repaired, dirt and sand can get into the pipe. The next time water runs, that grit travels to the valves and lodges under the diaphragm, so it can't seal.

If a zone started running on after pipe work, suspect debris first. The grit may still be in the line, so cleaning one valve may not be the end of it. Check every zone after a repair.

What not to do

• Don't leave the zone running. It wastes water and can flood beds and lawn.
• Don't force the bleed screw or solenoid. Snug by hand is enough. Overtightening can crack the parts.
• Don't open a valve with the water on. Shut off the system first.
• Don't keep replacing the solenoid. If the cause is grit or a bad diaphragm, a new solenoid won't fix it.

When to call us

Call us if:

• The zone still runs after you've closed the bleed screw and cleaned the valve.
• The diaphragm is torn or the valve body is cracked.
• More than one zone is acting up.
• You can't find the valve box or shut off the water.

See irrigation repair or contact us.