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Probably a failed zone control valve. It needs to be found and fixed.

Generally, when the problem is isolated to a single zone, any of the following could be a problem

• No power out at zone terminal
• Cut wire (“open circuit”)
• Shorted wire (“short circuit”)
<font color="red">• High resistance (bad splice)</font id="red">
<font color="red">• Solenoid “shorted” or “open”</font id="red">
<font color="red">• Diaphragm assembly failing</font id="red">
• Solenoid exhaust port completely obstructed
• Flow control on valve shut

The problems in red are the most common causes of single valve failure and is probably the case with your system. Locate the valve and check for the above issues.

<font color="red">It is important to turn off or close the water main and drain the irrigation line completely before disassembling a valve. Open the bleed screw on the top of the valve to relieve any remaining water pressure.</font id="red">

To disassemble the valve, depending on make and model, first you must unscrew the solenoid from the valve (make sure water is off). Once the solenoid is removed, simply remove the screws on the top of the valve, or if it is a jar top valve, simply unscrew the whole top of the valve. (Note, if you have metal screws on top of the valve, it is NOT a jar top valve. Once the screws have been removed, simply lift the top off of the valve. Fairly easy even for a novice.

Valve repair kits are available that supply the important parts to the unit. Despite the daily hammering and rushing of water through an electronic valve, they are reasonably durable. With proper maintenance and repair, electronic control valves will sustain the integrity of the irrigation design for years.

If you decide not to fix the problem yourself, you are probably looking anywhere from $40-60 an hour labor, plus parts. Generally, a valve replacement shouldn't take more than a couple of hours.