Question
Hi. I have an existing system, but one of my zones has lost the majority of its pressure or fails to come on at all. I have a Hardie solenoid valve. I have changed solenoids and borrowed one from another zone to try, with the same results. I have opened the bleed valve (? small screw on the top) and the zone comes on full pressure, but when I close the bleed valve (?) I can hear the pressure reduce and then shut off. The solenoid continues to hum but I get no water or very little. Any ideas? Thanks,
Pat

Answer
Chances are that you have a problem with the diaphragm inside the valve.  These are a little tricky to replace, but can be done with care.  Also clean out the ports (the little holes) in the valve body.  If this doesnt work, then you will probably need to replace the valve.