TL;DR: Most sprinkler zones that stop working fail above ground, not under it. Check the controller program first, then run the zone manually at the valve. If the valve opens by hand but not from the controller, it’s typically the solenoid or the wiring as the usual suspect — all generally fixable without digging up the lawn.
Work through these steps in order
- Rule out the controller. Make sure the zone actually has run time in the active program, the date and time are right, and the controller isn’t in rain-delay or “off”. A rain sensor that’s stuck wet will silently hold zones off — bypass it for one test cycle if your controller has that switch.
- Run the zone manually from the controller. Use the manual/test function for that one station. If it runs manually but not on schedule, the problem is the program, not the hardware — fix the schedule and you’re done.
- Open the valve by hand. Find the valve box for that zone and either twist the solenoid (the black cylinder with two wires) a quarter-turn counterclockwise or lift the bleed screw. Water on: the plumbing side is healthy, and the problem is electrical. No water even by hand: the valve diaphragm is stuck or a shutoff feeding that manifold is closed.
- Test the solenoid. With the controller commanding the zone on, listen and feel for the solenoid click. No click: swap its two wires with a zone that works. If the dead zone now runs, the wiring or controller terminal is at fault; if it still doesn’t, replace the solenoid — it unscrews by hand, no digging.
- Check the wiring and the common wire. One zone dead is usually that zone’s wire; several zones dead usually means the shared common wire or a blown controller fuse. Wire splices in valve boxes fail far more often than buried wire runs — look there before suspecting the yard.
- If water flow is weak rather than absent, that typically indicates the valve is failing and it’s time for a replacement. Weak flow across the whole zone can also mean a leak on that line — soggy spots or abnormal runoff point there.
When it really is underground
If the valve opens by hand but water is not coming from the nozzles, or one section of lawn is mushy, the lateral line or a fitting below grade is the likely failure. Even then, a repair usually means opening one small, targeted hole at the failure point — not trenching the yard. That diagnosis is where a pro pays for itself: we test at the valve, isolate the section, and open only what needs opening. If that’s where you’ve landed, our sprinkler repair crew in Thousand Oaks handles exactly this, every week.
Common questions
Why does one sprinkler zone work but the next one won’t?
Each zone has its own valve, its own solenoid, and its own wire back to the controller. When a single zone dies, one of those three is almost always the cause — shared parts like the pump, main line, or common wire would take out every zone at once.
How do I tell if it’s the controller or the valve?
Open the valve by hand. If water runs, the mechanical side is fine and the fault is electrical — controller, wire, or solenoid. If nothing runs even by hand, the valve itself (or a closed shutoff) is the problem.
When should I stop and call someone?
If you’ve confirmed power at the controller, swapped solenoid wires, and hand-opened the valve and the zone still won’t run — or if fixing it means cutting pipe — that’s a fair place to hand it off. A crew that does this daily carries the valve parts on the truck and can usually sort a dead zone in one visit.