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Steam radiator valve leaks

My valve leaks but not at the stem or nut. It’s shown in the picture. It seems to be tight. But has a slight leak as a visible hiss. Can I pack it, gasket or other repair? Or do I need to replace the valve? 


  • mattmia2
    mattmia2 Member Posts: 9,655
    gasket, various locktite products, dope or tape.
  • Jamie Hall
    Jamie Hall Member Posts: 23,310
    Before you take it apart completely... back the packing nut off slightly. Open the valve -- doesn't have to be all the way. Now back the cover off half a turn or so. Once that far backed off, it should turn in both directions smoothly, though possibly not easily. If so, try just retightening it -- but don't be a gorilla You can distort it. Then tighten things up again.

    Still leak? Loosen things up again, but this time remove the cover completely. Make sure the mating faces are completely clean. You can put a very small smear of gasket compound (e.g. Permatex) on the mating faces, but don't overdo it. Reassemble.

    Note that it is not all that hard to cross thread it. If you do... it's toast.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • nicholas bonham-carter
    What’s your actual measured pressure?
    at the low pressures (ounces), needed in these systems, no hissing should be heard.—NBC