The best way to locate valve boxes is usualy to have a map made when you install the system. Barring that, in the four soccer venues I control, all the valves are directly in line with the sprinkler heads. If you can locate one valve box, you can usually triangulate to the others
I use 24 volt 2 in valve heavy duty solenoids on my soccer fields. Does anyone have a good source for purchasing just the solenoids and not the entire valve? Thanks