I had an irrigation system installed several weeks ago using Hunter pgp heads and Irritrol 2400T valves. The water supply is well water. I've had a problem with one zone that usually will not completely shut off. My installer is very responsive and shows up every time I call him but I really don't think he knows what is causing it. He has thus far cleaned the valve several times, replaced the diaphram and replaced the entire valve twice (so this is the third valve). When he leaves, it is working fine. But after it sits for a few hours or overnight and then kicks on, it will continue leaking out of one or two heads until I open the manual bleed and shut it again. It is not just the draining of the water in the line. It will run all day and night until I shut it down. The flow is enough to bubble up from two heads. The solenoid appears to work fine but even that was replaced twice with the valve. Any suggestions?