How to Check the Solenoid on a Valve for an Irrigation System

Unscrew the valve solenoid, located on the top of the valve, to allow water to flow through. The knob-like solenoid can be unscrewed by turning counterclockwise to release air pressure from inside the valve. Once the air pressure is released, the water flows through the valve diaphragm and out of the valve to the sprinklers. Once the solenoid is open, the sprinklers pop up and water the lawn.

Twist the valve solenoid closed to shut off the flow of water from the main irrigation line to the sprinklers. Twist the valve completely clockwise to close it. The flow of water to the sprinklers should cease completely. If water continues to dribble from the sprinklers, there may be debris or blockage below the solenoid.

Open the irrigation timer box to expose the control panel. Press the button or turn the dial of the timer to manually water the lawn. When the timer is set to water manually, an electrical signal is sent from the timer to the valve solenoids, causing them to open. When the valves open, all sprinklers in the lawn pop up and water. If all or some of the sprinklers don't water the lawn, there might be a problem with the valve solenoid components or the timer wiring.

Press the button or twist the dial on the irrigation control panel to activate each valve or station one by one. If one of the solenoids fails to open, the solenoid or wiring from the irrigation timer might be compromised.

Turn off the main irrigation line. Unscrew the valve solenoid counterclockwise completely to determine whether water pressure going through the valve is low, the valve fails to open or the valve fails to close. Lift the solenoid out from its position and remove the filter and plunger from below it. Clean out any debris, dirt or other blockage from inside the solenoid chamber by hand or with water. Clean the filter and the plunger with your hands and water, then put them back in place. Screw in the valve solenoid clockwise to close it. Turn the irrigation main line back on and activate the solenoid from the irrigation timer.