Low Pressure in One Zone
Using Irratrol valves for that are 20 years old for 5 zone system. Four zones are working fine but zone 5 is not getting enough pressure to fully extend the heads and when pulled up by hand water does not extend more that a couple of feet. Water flowing to valve is adequate, (when bonnet was removed this could be observed). Removed each head individually and water is coming out but without much pressure ie it is not shooting in the air. Replace diaphram and this did not solve the problem. Switched solenoid with adjacent zone that was working fine and this did not solve problem. When I turned the bleeder valve a small amount of water comes our but it doesn't seem to affect the system. When I slightly unscrew the solenoid water comes out. The stem on the valve is fully turned counter clockwise which is the open position. When I turn the stem fully clockwise, the closed position, water still comes out of the head. I suspect the problem is with the valve and hopefully not a broken pipe. I see no visual evidence of a leak.
Any help or advice would be greatly appreciated.