My lawn sprinkler system has 4 zones and I noticed that one zone is staying on all the time. Even if I set the timer controller to off position, that valve stays on. If I unplug the controller, the valve shuts off. I tried doing a reset on the controller and it made no difference. Do I need to replace the controller?
Lawn sprinkler stays on
sprinkler-system
Related Solutions
First we need a Manufacturer and possibly if you can find it, a model number. Irrigation control valves like this have two parts, a diaphragm operated water control valve and a vacuum breaker. Typical Rainbird system shown here.
The control valve uses an electrically controlled needle valve that operates the main diaphram valve through servo action (small force controls large force). Cross section to give an idea how this works. When the needle is seated, full water pressure operates on the upper side of the diaphragm, shutting water flow off. When the needle opens, the pinhole in the diaphragm is smaller than the needle opening, pressure dumps and the diaphragm opens.
Where your leak is occurring is in the vacuum breaker (right hand side below). This device operates to prevent water siphoning back into the water line through the control valve if water pressure drops. It is essentially a check valve with one side open to the atmosphere that closes under pressure and if the parts are damaged through wear, foreign object stuck in the seat, corroded in place, etc. becomes as you've found, a large volume leak under pressure.
This is where having all that manufacturing information is important as most of these can be repaired if you can find the repair kits. Otherwise, it's complete replacement time.
Exploded diagram of the above example Rainbird unit less the solenoid control.
Champion Classic Brass 3/4" Automatic Actuator and Anti-Siphon with Union
Manufacturer is Arrowhead-Champion http://www.championirrigation.com
I've used Irrigation Direct for other product, their replacement parts page. There are other businesses listed. If you have a large irrigation supply anywhere near, they probably carry the product. Arrowhead is a well known manufacturer of brass plumbing fittings.
The Champion product has been around in manual systems since the 1930's. To get the Vacuum Breaker loose, you might need gentle heat on the body. Keep it on the breaker side.
Breakdown of the original Manual Valve and Anti-Siphon with Union
And the bits in the Anti-Siphon Valve that are giving you grief
You would not use the existing good sprinkler wires to bring the 120VAC out to the valve box. The wires are not rated and approved for that type of use. Place the converter transformer indoors to step the 120VAC down to the 24VAC. The "good" wires could then be used to route the 24VAC outdoors.
I would not use the sprinkler timer in the valve box. It would be very inconvenient to use it in that manner and the underground environment is highly likely to not be friendly to the control unit circuitry. Instead you should install an outdoor timer unit on an exterior wall above the valve box. (Use "outdoor sprinkler timer" in Google to see a selection of possible timers). The better outdoor timers have a lid that closes over the controls to protect the interior from the elements. You could then use a PVC conduit to route the necessary wires from the timer down into the valve box to keep things neat.
Do select the timer as one that works off the low voltage.
Best Answer
Turns out the controller is working correctly again after leaving it unplugged for a day. It is possible it went haywire after getting wet from one of the adjacent sprinklers that was misadjusted. I adjusted the sprinkler and put a plastic bag over the controller until I can replace it with a proper outdoor controller model (as the previous owner used an indoor model with no cover.)