CSLB C-27 Landscaping ContractorIrrigation SystemsMedium
A landscape contractor is performing a spring start-up for an irrigation system that has been winterized. After opening the main shut-off valve, the contractor notices a continuous, low-volume flow of water coming from one of the sprinkler heads in a zone that is currently off. All other zones are functioning correctly. What is the most probable cause of this issue?
- AA stuck-open solenoid on the zone valve
- BA clogged filter at the main backflow preventer
- CInsufficient water pressure in the mainline
- DA broken lateral line in that zone
Show answer & explanationAnswer & explanation
Correct answer: A. A stuck-open solenoid on the zone valve
A continuous low-volume flow from an 'off' zone's sprinkler head typically indicates that the zone valve is not fully closing. This is most often caused by a stuck-open solenoid, which prevents the diaphragm from seating properly, allowing water to trickle through.
Why the other options are wrong
- B. A clogged filter would reduce pressure to the entire system or downstream zones, not cause a specific zone to leak when off.
- C. Insufficient pressure would result in poor spray or no pop-up when the zone is on, not a continuous flow when off.
- D. A broken lateral line would cause a larger leak, usually at the break point, not a continuous low flow from a head.
Stuck-Open Solenoid
A solenoid on an irrigation zone valve that remains energized or mechanically stuck in the open position, preventing the valve diaphragm from seating and causing continuous water flow to the zone.
- Prevents the valve from closing fully
- Results in continuous trickle/drip from heads in that zone
- Can be due to debris, electrical issue, or mechanical failure
- Requires cleaning, repair, or replacement of the solenoid/valve
Memory trick: Trickle from an off zone? Solenoid's stuck, not letting go.