A bad sprinkler valve shows one of four signs: the zone won’t turn on, the zone won’t turn off, water pools around the valve box, or you hear clicking but no water flows.
The Short Answer
A bad sprinkler valve almost always reveals itself through one of four symptoms. The zone will not turn on at all. The zone will not turn off and runs continuously. Water pools around the valve box even when the system is off. Or you hear the solenoid clicking when the zone activates but no water flows to the heads. Any of these signs points to a valve problem — or the wiring that controls it.
What a Valve Does
An irrigation valve has two main parts: the solenoid and the diaphragm. The solenoid is a small cylindrical coil sitting on top of the valve. When it receives 24 volts from the controller, it becomes an electromagnet and lifts a small plunger, opening a pilot port. Water pressure then pushes the diaphragm — a rubber disc inside the valve body — upward, opening the main water path to the sprinkler heads. When the controller stops sending voltage, a spring closes the plunger, the pilot port seals, and water pressure pushes the diaphragm back down, shutting off the flow.
A failure in either the solenoid or the diaphragm — or the wiring between the controller and the solenoid — produces one of the four symptoms below.
The Four Signs of a Bad Valve
- The zone will not turn on — The solenoid is dead, the wire is broken, or the controller output is not reaching the valve. The diaphragm could also be stuck closed from debris.
- The zone will not turn off — The diaphragm is stuck open, often from debris, sand, or mineral buildup. The solenoid plunger may also be stuck in the open position. This is the most urgent symptom because it wastes water continuously.
- Water pools at the valve box — The valve body itself has cracked, or a fitting connecting to the valve is leaking. This can happen from freeze damage, root intrusion, or age.
- Clicking but no water — The solenoid is energizing (you can hear it click) but the diaphragm is not lifting. This means the solenoid works electrically but the valve’s internal mechanism is stuck.
- Weeping between cycles — The valve slowly leaks water to the heads even when the zone is off. A worn diaphragm or debris on the valve seat prevents a full seal.
How to Test a Valve
You can narrow down the problem with two simple tests. First, open the valve manually using the bleed screw or solenoid on top of the valve (turn it a quarter turn counterclockwise). If water flows, the valve body and diaphragm are working mechanically — the problem is electrical. If no water flows, the valve is stuck or the water supply to that valve is shut off.
Second, if the valve works manually, test for voltage at the solenoid. Set a multimeter to AC volts and place the probes on the two solenoid wires while the controller runs that zone. You should read 24 to 28 volts. If you see voltage, the solenoid is bad and needs replacement. If you see no voltage, the problem is the wire or the controller output — not the valve itself.
You can also test the solenoid’s resistance with the power off. Set the multimeter to ohms and measure across the two solenoid terminals. A good solenoid reads 20 to 60 ohms. A reading of infinity or zero means the coil is broken or shorted.
Valve vs. Wiring vs. Controller
The hardest part for most homeowners is figuring out whether the valve, the wire, or the controller is the culprit. The manual bleed test and the voltage test together tell you. If the valve works manually but you have no voltage at the solenoid, the problem is the wire or the controller. If you have voltage at the solenoid but the zone still will not turn on, the solenoid or diaphragm is bad. If the valve does not work manually at all, the valve itself is the problem.
A valve that will not close wastes more water than any other sprinkler problem. If a zone runs continuously and you cannot shut it off at the controller, shut off the water at the main valve and call for repair. Every hour it runs unchecked can waste hundreds of gallons.
If you suspect a bad valve, our sprinkler repair technicians can test every valve in your system, identify the bad one, and replace it in a single visit.
