(I am a newbie to sprinkler system repair, I would appreciate your advice). I have an in ground sprinkler system at my residence. They said it was commercial quality when it was installed (about 20 yrs ago). Well, I have noticed that now one of the sprinkelers (a small pop up one) in zone 1 of the system stays on even when the timer is up in that zone (only two sprinklers in that zone, the other one leaks very slowly). it stays on until I shut off the water to the entire system. All the other zones work perfectly. So what type of problem am I looking at, a bad head, problems with the timer, or problems with the valve that is controlled by the timer. (I am leaning towards the valve) I can get pics if that helps.