How to repair a sprinkler that won’t shut off

Determine which valve needs to be replaced.

1. With sprinkler system on, manually turn on each valve, one at a time.  When a valve turns on an additional zone, you know that's not the problem valve.  Shut it off and move on to the next one.
2. Turn on the valves, one at a time, and when you find the valve that does not turn on any additional sprinklers, that is the valve that will not shut off.
3. Turn off the water supply to the sprinkler system.

Replace inner valve parts.

1. Disconnect the two wires connected to the sprinkler valve and note where they are connected.  One should go to a group of wires; this would be the common wire.  The other should go to a single wire; this would be the power wire for that valve.
2. Unscrew the ring at the base of the sprinkler valve and remove the valve.
3. Remove the rubber piece and ring from valve base.
4. Check inside the valve body (the part that's connected to the sprinkler system) for foreign objects, sand, etc. and remove if any.
5. Open the new valve and remove the ring and rubber base.  Be careful not to lose the spring that is also inside.
6. Place the ring in the existing sprinkler valve body
7. Place the rubber piece on the ring.
8. Place the spring on the center of the rubber piece, and carefully put the new valve on top.
9. Screw the ring on and secure the valve.
10. Turn the valve to the off position.

Make sure the problem is fixed

1. Turn on the water supply to the sprinkler system.  If no sprinklers come one, the problem is most likely fixed.
2. If sprinklers do come on, either the wrong valve was fixed or you have multiple valves with a problem.
3. Turn on the repaired valve manually and ensure that the sprinklers come on, then turn it off.

Connect the wires

If the valve is functioning correctly, you can connect the wires.  Waterproof wire-nuts are recommended.  Once the wires have been reconnected, turn on the sprinkler zone with the sprinkler control panel.  If the sprinklers come on and shut off with the control panel, the problem has been fixed.  If not, more troubleshooting is needed to determine which valve needs to be replaced.