If one sprinkler zone keeps flowing after its scheduled run, first make sure the controller has actually stopped commanding it. When the controller is off and the water continues steadily, the zone valve may be passing water because it is not closing fully, or because it is still receiving an electrical signal. Checking the display, observing the flow, and comparing the affected zones can narrow the likely cause before anyone works on the system.
Confirm the controller has stopped the zone
Start at the controller rather than assuming the displayed time means the irrigation cycle has ended. Check whether a manual run is still active, then review the program’s start times and active schedules. Some controllers operate several zones in sequence after a single start time, so another zone in the program can begin when the one you were watching finishes. If a second start time is programmed, a zone may also run again later than expected.
Set the controller to off and observe the sprinklers. A steady, continuing spray or stream is different from a brief tail of water draining out of low sprinkler heads after a cycle. The latter can happen as water already in the piping drains; it should taper rather than behave like a zone that remains under flow. Note how long the water continues and whether it stops completely. That observation helps distinguish an active irrigation command from water still emptying from the lines.
If the runtime differs from what you expected, check whether a seasonal adjustment is changing the programmed watering duration.
Understand what can keep a valve open
A common automatic sprinkler valve uses a flexible diaphragm and a sealing surface, often called the seat, to stop water. During a commanded run, the valve opens; when the command ends, the mechanism should return to its closed position. Grit caught where the diaphragm seals, a worn part, or damage can leave a small opening. Water then continues through that zone even though the controller is no longer asking it to run.
A manual bleed control is another possibility. Many valves have a way to open them manually for testing or operation. If that control is left open, water may keep flowing without a normal controller command. The location and design of controls vary, so do not force a knob or screw whose purpose is unclear. A valve that needs cleaning or repair is different from one simply left in a manual-open position.
Electrical control is a separate path to the same symptom. A solenoid is the electrically operated part of the valve; if it remains energized, the valve can continue to receive an open command. That may relate to controller output or wiring rather than debris at the sealing surface. These causes can look alike from the lawn, which is why the controller status and the number of affected zones are useful clues—not a definitive diagnosis by themselves.
Use the number of affected zones to guide the next check
When only one zone continues running, focus attention on that zone’s valve and its control wiring. When several zones run unexpectedly, the shared controller schedule or another common control issue deserves attention first. The distinction is practical: several unrelated zone valves developing the same symptom at once is a different pattern from one isolated zone that will not shut down.
If water keeps flowing, locate the irrigation system’s water shutoff and close it to limit waste while the cause is identified. If the shutoff is not clear, avoid turning unidentified plumbing controls. For a repair discussion, record the zone number, what the controller displayed, whether the flow was steady or fading, and whether closing the irrigation shutoff stopped it. Those observations describe the symptom without guessing whether the fault is electrical or mechanical.
Brother's Irrigation & Lighting is based in Knoxville.
