Sprinkler Zone Won’t Turn Off: What Causes a Stuck Valve

A sprinkler zone that will not shut off is one of the few sprinkler problems that needs attention right away. It can run all night, flood part of the yard, send water into the street and add up on your bill. This article explains how to stop it, then how to find the cause.

First: Stop the Water

Before you troubleshoot, stop the flow:

1. Turn the controller off. If the zone stops, the problem is likely the controller or its programming.
2. If it keeps running, close the irrigation isolation valve. It is usually between the water meter and the backflow preventer.
3. If you cannot find it, close one of the shutoff valves on the backflow preventer.

Once the water is off, you can work on the cause without wasting water.

Is It the Controller or the Valve?

This is the first question to answer. Turn the controller off or unplug it.

• If the zone stops when the controller is off, the controller was sending power when it should not. Check the program for extra start times, multiple programs, or a manual run that was left on.
• If the zone keeps running with the controller off, the valve is stuck open mechanically. The problem is at the valve.

Controller Causes

Overlapping programs or extra start times

Many controllers have several programs, each with several start times. It is easy to set a start time by mistake, or have two programs that water the same zone. The zone may look like it never turns off when it is actually starting again and again. Our guide to controller programming explains how to review and clean up programs.

A failing controller

A controller with a shorted station output can send power to a valve all the time. If the zone only stops when you unplug the controller, and the program looks correct, the controller may need repair or replacement. See our guide to a controller that is not working.

Valve Causes

Debris in the valve

A small piece of grit, sand or pipe shaving caught between the diaphragm and the seat keeps the valve from sealing. This is the most common cause, especially after a pipe repair. Shut off the water, remove the bonnet, rinse the diaphragm and seat, and clear the small ports.

A torn or worn diaphragm

A rubber diaphragm with a tear, a stretched spot or a hardened edge can let water pass even when the valve is supposed to be closed. Replacing the diaphragm usually fixes it.

An open bleed screw

Valves have a bleed screw or lever for manual testing. If someone opened it and did not close it, the valve stays open. Check that it is tight.

A stuck solenoid

The solenoid’s plunger can stick in the open position because of debris or wear. Turning the solenoid a quarter turn counterclockwise opens the valve manually on many models; turning it back closed can sometimes reseat it. If it keeps sticking, replace it.

The flow control is backed out too far

On some valves, a flow control stem that has been unscrewed all the way can keep the valve from closing properly. Turning it back in partway can help.

When It Is Not a Stuck Valve

If water keeps coming out of the lowest head on a zone for a few minutes after it stops, that may just be water draining from the pipe, called low-head drainage. It stops on its own. A valve that is truly stuck keeps running at full strength. Our article on low-head drainage explains how to tell them apart.

Why Valves Stick More Often in Some Yards

Systems that have had many pipe repairs, systems on older mainlines, and systems that were not flushed after work tend to have more debris. Clay and mud getting into open pipe during repairs is a common source. Valves that sit low in flooded boxes can also collect sediment.

Preventing a Repeat

• Flush pipe thoroughly after any repair before reconnecting valves or installing nozzles.
• Replace diaphragms on older valves before they fail.
• Keep valve boxes clean and dry.
• Consider a master valve if your system does not have one. A master valve stops flow to all zones when no zone is supposed to run, which limits damage from a stuck zone valve. Fort Worth’s irrigation rules call for a master valve on new installations.

Checking the Damage After a Long Run

If a zone ran for hours before you caught it, walk that area once the water is off. Look for washed-out soil around heads, water standing against the foundation, and puddles in beds. Let the area dry out before you mow or walk on it heavily, since saturated clay compacts easily. Skip that zone’s next scheduled cycle, since the soil will already hold plenty of water. If water ran into the street, it is a good idea to fix the valve before the next watering day so the runoff does not repeat.

It also helps to check the controller’s clock and program at the same time. A power outage or a reset can scramble start times, and it is worth ruling out before assuming the valve is the only problem.

When to Call a Technician

If you have cleaned the valve and it still will not close, if you cannot find the valve, or if you cannot shut off the water, a technician should take over. Our guide on sprinkler valve repair explains how valves work, and our sprinkler repair team can repair or replace the valve.