How Does an Irrigation Zone Valve Operate?

Parts

• An electronic irrigation zone valve consists of two chambers, a diaphragm, a couple of springs, a plunger and a solenoid. Water flows from the inlet side of the valve and fills the first, lower chamber. Water is retained there by a diaphragm in the upper chamber, where a spring provides minimal pressure against the water pressure coming from the lower chamber. The remaining pressure is supplied by a small air hole from the solenoid plunger that's connected to the upper chamber. The plunger traps air into the upper chamber and pushes down the diaphragm, creating the extra pressure needed to seal water in the lower chamber.

Operation

• When the irrigation controller sends an electronic signal to the solenoid, a small spring in the solenoid causes a rubber plunger to lift up and allow airflow into the upper chamber. Air pressure then drops within the upper chamber, causing water pressure from the inlet to be too great for the sealing diaphragm. Inlet water flows past the diaphragm and through the irrigation valve outlet to the sprinklers.

Timer

• If the irrigation valve is activated electronically, the solenoid opens when the irrigation controller reaches a scheduled activation time and sends a signal to the valve solenoid. A common wire and a color-coded wire are each connected to the electronic valve's two solenoid wires, allowing the irrigation controller to open and close.

Manual

• Some irrigation zone valves are controlled by hand and feature no connected electronic timer. In this event, the valve can be opened if you unscrew the valve solenoid by hand. When the solenoid opens, air pressure is lost within the upper chamber, allowing the water to spill into the valve outlet and activate the sprinklers. During winter, you'll want to drain the valves during hard freezes to avoid system damage. Unscrew the solenoid and the bleed screw, which is located on top of the valve just in front of the solenoid.