CSLB C-27 Landscaping ContractorIrrigation SystemsHard
A landscape contractor is called to a commercial site where the irrigation system's backflow preventer is leaking continuously from its relief valve. The leak occurs even when no zones are actively running. What is the most likely cause of this issue?
- AThere is a significant break in a lateral line downstream from the backflow preventer.
- BThe backflow preventer's check valve or relief valve assembly is fouled or damaged.
- CThe irrigation controller is continuously sending power to a zone valve.
- DThe system's main shut-off valve is partially closed.
Show answer & explanationAnswer & explanation
Correct answer: B. The backflow preventer's check valve or relief valve assembly is fouled or damaged.
A continuous leak from the relief valve of a backflow preventer, especially when no zones are running and there's no demand downstream, almost always indicates an internal failure of the backflow preventer itself. This is typically due to debris preventing a check valve from seating properly or a damaged relief valve assembly, allowing water to escape.
Why the other options are wrong
- A. A significant break downstream would cause water to exit the break, and while it might affect pressure, it wouldn't directly cause a continuous leak from the relief valve of the backflow preventer when the system is static.
- C. If the controller was powering a zone valve, that zone would be running, and the leak would likely be from the zone itself or exacerbated by the flow, not primarily from the backflow relief valve when no zones are running.
- D. A partially closed main shut-off valve would reduce overall system pressure/flow but wouldn't cause a backflow relief valve to leak continuously when the system is off.
Backflow Preventer Relief Valve Leak
A leak from the relief valve of a backflow prevention device, typically indicating a malfunction of its internal check valves or the relief valve assembly itself.
- Commonly caused by debris, worn seals, or damaged springs.
- Requires professional repair or replacement to ensure water safety and prevent waste.
- Occurs even when irrigation zones are off if the internal components fail to hold pressure.
Memory trick: Backflow's crying, even when nothing's flowing, its own parts are showing!