One of the zone control valves in my heating system does not appear to be working. The thermostat is calling for heat, but no water is flowing. If the other thermostats call for heat, the valves seem to open as the pipes above the valve get hot from the water flowing through. The one that appears busted gets luke warm at best. All 4 valves in the system are fed from the same pipe, and the failed valve is the third in the series of 4 along the pipe (and #4 flows fine) so it doesn't appear to be something in the feeder pipe.Is there anything I can do to try and fix the existing valve, can I replace the valve myself? Would replacing the valve top of the valve (the green/gold portion) possible fix the issue (maybe a problem with the operation of the piston? Is there anything I ahve to do before removing the valve top aside from removing power to the valve?
The first thing is to see if the zone valve is getting voltage from the thermostat telling it to open. Most are low voltage a/c current. If it is getting power and not opening you probably should change out the entire valve. Some have compression fittings and some have a solder connection. If it is a solder connection make sure the valve is open before you sweat it . You will have to turn off the water supply to the valve and the power and bleed off the pressure. Make sure the solenoid matches the existing voltage. Have fun.
if you have a circulating pump .shut it down [as well with the electric switch to the boiler] follow both pipes coming and going from the boiler shut any valves thus isolating the manifold slowly remove the zone valve .there will be a little water leaking out .replace valve amd hook up electric to valve .before u do all that take two jumpers and jump out the valve to another .see if u have a bad cir cut
By your description it sounds like you have a Taco zone valve, if so, you can twist the top, (head) and it disconnects from the valve body, you could swap it with one of the others to prove good or bad before you buy one, there not cheap.
You would need to isolate the valve from the line, and depressurize the system, and I would think that turning off the heater and letting the temperature fall would probably be necessary if you don't want a relief to lift in the boiler. If you make a mistake here you have a very good chance of being scalded to death, or permanently scarred. Also, you may need to sweat and braise the new valve with a torch, so you had better be sure you know what you are doing and don't burn your house down.
