When a Solenoid valve fails to close, letting the water flow to you designated irrigation zones, it is probably due to something like a foreign material stuck within it. This could be a tiny pebble, dirt, grain of sand or even a tiny insect. At this point, to fix the defective solenoid, you’ll need to take it apart and clean the sensitive areas of it.
Disassembling the solenoid may be the easiest part, but you have to be mindful, keeping track of what screws and parts go where, as putting back it all together after cleaning, will still make it malfunction if out together incorrectly.
Once you unscrew the solenoid cap, unscrew the plunger, making sure you have a good grip of this part so as not to lose it. Also, when opening the valve, be particularly careful of not losing the small spring, so get this spring and it keep it in a safe spot.
Once you’ve cleaned out the solenoid valve, put it back together the way you originally opened it. Once you put everything back together, try it out to see if it works correctly. If it works just fine, you’ve successfully repaired your faulty solenoid valve.
However, if you do not feel confident in your ability to fix a faulty solenoid, it is just best to hire irrigation experts to tackle your problematic solenoid valve.