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What kind of radiator valve is this?

Heaterton Member Posts: 12
Hi everyone. Long time lurker first post. I was wondering if anyone could help me identify this radiator valve? (As in, what fitting is the male part?)


  • mattmia2
    mattmia2 Member Posts: 8,893
    It connects it the other half of the union it came with.
  • Heaterton
    Heaterton Member Posts: 12
    Thank you. That's still in the radiator. Is there a name for it and maybe I could buy a cap for it or even convert it to NPT?
  • Jamie Hall
    Jamie Hall Member Posts: 22,182
    The entire fitting -- the half you are holding and the other half, which has the nut on it, is called a union. There is no name for the two halves. The two halves go together, and are mated with each other. The seal is on the smooth end face of the fitting, not on the threads.

    In this particular instance, the complete fitting is the valve -- which you are holding -- and the spud, which is still in the radiator.

    The thread you have is not a pipe thread. There is a remote chance -- very very remote -- that you might be able to find a matching union with a male NPT on the other end of the female half, put that on, and put a cap on that (i you could get the spud out of the radiator without damage, that is just such a piece). Since the mating faces of the union are unique to the maker and size, that's a pretty slim chance.

    What, then, I would ask, is the purpose of the exercise? If it is to cap off an unused radiator connection, your best be is going to be to remove the whole valve from the connection and cap that. If you go that route, be sure to use a backup wrench on the riser, so as to avoid unscrewing the riser from whatever is next in line below it -- which can ruin your whole day.

    If you want to use the valve and attach to a new radiator, as I noted above you first try will be to get the spud out of the old radiator. Sometimes that works. Usually it doesn't, but it's worth a try. If it does, get a new radiator valve which will come with the matching spud.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Heaterton
    Heaterton Member Posts: 12
    Thank you Jamie for the very detailed explanation. Yes it was to remove an unneeded radiator.

    I figured it was a union but assumed incorrectly I could get a matching cap for it to thread on.

    I am simply learning the trade while my HVAC school is on covid break...

    I had to sweat out the elbow and solder a cap on. I appreciate the help and info!