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Leaking Steam union

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mtlight
mtlight Member Posts: 28
in THE MAIN WALL
I developed a leak in a steam union that I cannot tighten any more. It’s only a drip but it’s the heating season and not sure if I want to deal with opening and closing and possibly disturbing the system. Any suggestion? Rtv silicone a possibility after a wire brush? Would do a complete fix after heating season. Thanks in advance

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    Take it apart and clean it. Make sure the alignment is ok. Coat the threads, face and seat with "never seize" or "anti seize" an auto parts or hardware store will have it.. Put it back together and crank it tight. If you have someone to lightly tap it with a hammer while your tighten it you will get it tighter.

    Look the union over if it's rusty or deteriorated you may want to call a professional as your drip could turn into a worse problem.
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    Keep in mind that the union seats -- and seals -- on the faces. You can, as @EBEBRATT-Ed said, put a thin coat of never seize on the faces -- but nothing else. The faces must be lean and smooth -- no scratches, no corrosion. Also, the pipes must be very closely aligned, both angularly and linearly. Unions aren't meant to compensate for or correct misalignment.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Fred
    Fred Member Posts: 8,542
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    @mtlight , you say a leaking"Steam union" Is this a union fitting or a flange union (two flat flange surfaces)? If a flange joint, there is a fiberglass gasket between the two flat surfaces. That mey need to be replaced, with a little high temp silicone sealant on the gasket faces for added assurance.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
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    For unions, I recommend dishwashing liquid on the faces. Anti-seize contains some particulate matter, which can hold the faces apart.--NBC
  • SlamDunk
    SlamDunk Member Posts: 1,580
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    Replace it. if torquing nut cant stop leak, teflon tape, dope, cleaning face/ seat may help but the leak will return at an even more inconvenient time. I just replaced a two inch and an a one and half in yesterday. I won’t have time on Thanksgiving or Christmas eve.
  • Paul48
    Paul48 Member Posts: 4,469
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    I agree.....Or you might be wasting your time, "trying to make a peanut into a phonograph needle" :smile:
  • mtlight
    mtlight Member Posts: 28
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    Ok thanks. Right now coming into the winter and the union is in a precarious spot where if I attempt to mess with the piping there could be a bigger problem if things don’t go well. Not a short cut guy big looking to plug it somehow through the winter without even disconnecting the union if possible. Then fix in the spring if possible. Thanks for the info.
  • Paul48
    Paul48 Member Posts: 4,469
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    Try that spray on rubber.....flex seal. There's two possible outcomes.
  • Distance
    Distance Member Posts: 6
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    I had this same problem. Used RTV Silicone and now it's working like a champ :)
  • mtlight
    mtlight Member Posts: 28
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    Snugged the union maybe 1/8 turn. Leaked a bit more for a few days on Long calls now all of a sudden stopped?
  • SlamDunk
    SlamDunk Member Posts: 1,580
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    My guess is pipes aren't aligned well or a nipple is a hair short from the original install they used high torque on nut to draw seat to face. If that's the case, they always want to pull apart and that 1/8 turn makes a difference. Sometimes corrosion will stop a slow leak.

    mtlight

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