Sprinkler valve malfunction

[ladmo19013]

I just had a sprinkler zone go off when the valve is not even electrically connected. It is disconnected both at the valve (both wires are capped off together) and the wire to the timer is not connected. How can that happen? I did notice that the timer had some strange reading on it - 30L - or something like that. I unplugged the timer and reset everything, checked to make sure the valve was still disconnected. This valve has been disconnected and not used in years, but today it just started pumping out water, and I had to turn off the water supply to the sprinklers to get it to stop.
Any ideas???

 

[Twowaxhack]

The valve failed. A solenoid valve doesn’t need power to fail and leak.