CSLB C-27 Landscaping ContractorIrrigation SystemsHard
A C-27 contractor is conducting a routine maintenance check on an irrigation system. The client reports that one zone is constantly running, even when the controller is off. Upon inspection, the contractor finds that the solenoid on the zone valve is receiving no voltage from the controller. What is the most probable cause of the valve remaining open?
- AA broken wire between the controller and the solenoid.
- BDebris lodged in the valve diaphragm.
- CThe controller's transformer has failed.
- DA short circuit in the common wire.
Show answer & explanationAnswer & explanation
Correct answer: B. Debris lodged in the valve diaphragm.
If the solenoid is receiving no voltage (meaning the controller is not telling it to open) but the valve remains open, it indicates a mechanical failure within the valve itself. Debris lodged in the diaphragm prevents it from sealing properly, causing water to continuously flow through the valve regardless of electrical commands.
Why the other options are wrong
- A. A broken wire would prevent the solenoid from receiving voltage to *open* the valve, but if the valve is already open and running without voltage, the issue is mechanical, not electrical activation.
- C. A failed transformer would cut power to the entire controller, preventing any zones from running, not just one zone running continuously.
- D. A short in the common wire would likely prevent multiple zones from operating, or cause the controller to trip, not a single zone to run perpetually without voltage.
Irrigation Valve Troubleshooting
Diagnosing issues with automatic irrigation valves, particularly when they fail to open or close as commanded by the controller.
- Solenoids control valve opening/closing via electrical signals.
- Diaphragms are seals that allow/prevent water flow.
- Common mechanical failures include debris, worn diaphragms, or broken springs.
Memory trick: No power, yet still it flows? Something's stuck, that's how it goes!