Sprinkler System Won't Shut Off: Valve or Controller Fault?

When a sprinkler system runs continuously unless the main water supply is manually closed, the fault lies either in a stuck valve or a controller sending constant power. Here's how to isolate the problem quickly.

Diagnostic Steps

1. Disconnect controller power. Unplug the 110V supply or turn off the breaker. If water stops flowing, the controller is malfunctioning (sending continuous 24V to the valve). If water continues, the valve itself is stuck open.
2. Identify the problematic valve. If you replaced "the valve" but didn't specify which—main shutoff or zone valve—confirm you addressed the automatic zone valve controlled by the timer.
3. Check indexing valve operation. If you must cycle water on/off to advance zones, the indexing valve is likely failing. These mechanical valves are prone to wear and often cause more trouble than they're worth.

Modern Solution

Replace indexing valves with individual electric solenoid valves per zone and a modern multi-zone controller. This eliminates mechanical complexity, improves reliability, and allows precise scheduling. Most contractors can retrofit this in a day.

Don't tolerate a system that won't shut off—it wastes water, damages landscaping, and indicates a fixable fault.