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Replacing radiator valves steam vs hot water? Size help?

Hello everyone! Well it's soon heating season and I need to do a few things before the heat is on. I have to change a few radiator valves for a hot water system. It is a 3 story house with 8 radiators. All the new replacement valves say steam but look like a hot water valve? Even Supply House has them all listed as steam valves. Is there a difference? Also is there a way to determine the size of the valves needed? They most likely are original and have no markings on them or anything. Reasoning for wanting to change some of them is to keep more heat downstairs. Last year the downstairs radiators were a little warm and the upstairs ones where hot, Some really hot. I was thinking to turn the upstairs ones down and let the downstairs ones open. I can't move most of the valves they are really old and down turn even with a pliers. I know its going to be a job to change the valves. Most will likely need to be cut out of the radiators.

Any help would be appreciated!


  • Jamie Hall
    Jamie Hall Member Posts: 23,442
    Ah... before you go to the trouble of changing the valves -- and trust me, it is trouble -- try loosening the bonnets of the offending valves (yes, they will leak -- you are going to have to take pressure off the system and probably drain it to do any of this) and see if you can free them up at all. if you can, it may be much easier to take the bonnet and stem all apart and clean them up and repack and reassemble them.

    If you do decide to change the valves, keep in mind that the spud which goes into the radiator is matched to the valve, and you need to replace them both together. The valve is sized by the pipe which it fits on... getting the old spud out of the radiator can,, once in a while, not be that bad. Usually it's an exercise in frustration. Be very careful when doing it to not damage the threads in the radiator.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,076
    I would try Jamie's suggestions first.
    Also, new valves usually are a little shorter than old.
    That is you need a little more pipe sticking out of the floor.
    Sometimes you can pull the pipe up, often not.
    I would check this out before going too far.