September 15, 2023
A sprinkler zone that won’t shut off is a different kind of urgent. While a dead zone just leaves your lawn dry, a stuck-open zone is actively wasting water — sometimes at a rate of thousands of gallons per hour — and it can put you in violation of San Marcos water restriction rules.
Sprinkler valves operate on a pressure differential principle. For a valve to stay open when the controller is off, something must be preventing the diaphragm from sealing.
A tiny piece of grit, a grain of sand, or a flake of pipe material lodging between the diaphragm and the valve seat is enough to prevent a full seal.
Diaphragms are rubber, and rubber degrades over time — especially in Texas heat.
Less commonly, the solenoid itself sticks in the energized position — physically holding the bleed port open.
Before blaming the valve, confirm the controller is not sending a continuous signal to the zone.
If a zone is running continuously: Turn the controller off completely. If the zone is still running, manually close the valve using the manual bleed screw. If you can’t close the valve manually, locate the main irrigation shutoff and close it. Call for service — don’t let a stuck zone run through the night.