Key takeaways
- Irrigation usually tees off the service line before the house shutoff, so the meter keeps moving with the house isolated even if the house line is fine.
- The irrigation shutoff is normally a valve just before the backflow assembly; close it and re-test.
- A backflow assembly keeps irrigation water from siphoning back into the drinking water; it is required on most metered systems.
- Winterized systems should be fully isolated; a mainline still pressurized to the first valve can leak all winter.
Where the irrigation connects
On most Kitsap properties with an irrigation system, the irrigation line tees off the water service line somewhere between the meter and the house, often near the meter or just inside the property line, and runs to a backflow assembly and then to the valve boxes. Because the tee is before the house main shutoff, closing the house shutoff doesn't isolate the irrigation. A meter test that shows flow with the house isolated could be the service line or the irrigation, and the next step is to isolate the irrigation separately.
Shutting it down for a test
There's normally a shutoff valve on the irrigation line just before the backflow assembly, sometimes in a box in the ground, sometimes above grade next to the assembly. Close it, confirm the controller isn't about to run a zone, and watch the meter again. If the low-flow indicator stops, the leak is on the irrigation side: the mainline, a valve or a lateral. If it keeps moving, the service line between the meter and the house is the problem and the irrigation is innocent.
What the backflow assembly does
A backflow prevention assembly, usually a double check or a pressure vacuum breaker on residential irrigation, keeps water in the irrigation system from siphoning back into the house supply and the public main if pressure drops. It's required on most metered systems and is tested periodically. It also has test cocks and shutoffs that make isolating the irrigation straightforward, and a leaking assembly itself is occasionally the culprit on a surprise bill.
Winterized systems
A system that's been blown out and shut down for winter should be isolated at its shutoff. If the shutoff is upstream of the backflow and closed, the mainline is unpressurized and can't leak. If the system was only shut off at the controller, the mainline is still pressurized to the first valve and can leak all winter, which is a common source of a high winter bill.
Written by the crew at 360 Leak Finders
We locate, excavate and repair buried water lines and exterior drains across Kitsap County, 24 hours a day. If this guide raised a question about your property, call (206) 354-9906.