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One Pipe Steam Radiator Supply/Shutoff Valve Leaking from Body, see pic

Dear All,
During the end of the heating season I saw steam leaking from the "body" of the radiator supply valve. It is labeled "G" in the attached picture. Not the packing nut. Is there a way to disassemble the valve body and repair this? Replace the gasket or use some dope on the threads? I wanted to tackle this before it gets cold.
It is a very small leak and I have to top off the water level about once a week during the heating season.
Thank you!


  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    If it really is coming from the threaded joint G, in principle you can unscrew that and clean everything up. Put some dope on the threads and screw it back together. Just like an old fashioned faucet or hose bibb. And, just like an old fashioned faucet or hose bibb, it may be somewhat reluctant to unscrew...

    While you have it apart, check the condition of the washer (E) and make sure everything else is in good shape.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,542
    Make sure you're steam pressure is not out of control too. Clean the pigtail, under the Pressuretrol and make sure the pressuretrol is working corectly. I saw a small leak from that area, years ago, on my system. I found my boiler pressure was running up to 5 or 6 PSI before the Pressuretrol would shut it down.
  • gerry gill
    gerry gill Member Posts: 3,078
    i would use pematex gasket sealer on that joint.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • scottie_2
    scottie_2 Member Posts: 14
    Dear All,
    I wanted to circle back on this issue to give you a conclusion, as I am sure a lot of issues posted do not update a result.

    I took a good look at this steam valve, it looks like someone put a pipe wrench on the part G, and deformed the seal. This valve was original to the house, as it matches all the others and was a nice nickel/ chrome under all the paint. It had been leaking a long time, as you could see the rust spot it created on the radiator cover, and also rust stains leaking down the pipe into the basement below.

    So, why would someone put a pipe wrench up high on the valve? Not sure but I suspect that whoever did that in the past was flipping the radiator orientation 180 degrees, from between two windows to under a window to be more space efficient?

    This was not caused by high steam pressure or a clogged pigtail.
    I replaced the valve and no more leaking.
    Thank you all for the help!