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Help with leak at union joining two lengths of pipe? (And what kind of union is this, anyway?)

Hi all,

I noticed some water on the floor of the crawl space under the 50+ (?) year old addition on the back of my 100+ (?) year old house. Took out the ceiling insulation and found this leaking union that splices together two pieces of pipe leading to a radiator in the back hallway. (see pics)

When I google "steam pipe union" I mostly find images of beefier unions with a big nut to tighten. But this seems quite thin and I'm not sure how it would even thread on/off since it doesn't appear to have flats for a wrench to grip.

Is this a DIY job to fix?

Many thanks in advance for any advice.




Comments

  • IronmanIronman Posts: 5,116Member
    edited October 2018
    That's a coupling, not a union. It looks like that entire section of pipe needs to be replaced. It's probably a wet return.

    Check the contractor locator above for a pro. It's definitely not a DIY project.
    Bob Boan


    You can choose to do what you want, but you cannot choose the consequences.
  • FredFred Posts: 7,910Member
    That's a coupling, not a union. The only way to tighten that up would be to take one section of the horizontal pipe loose from one end or the other, or, if you're lucky find a real union somewhere along that line, uncouple that union and try to tighten this couipling up. You may have to take that coupling off, use some pipe dope and then tighten it up.
  • the ill postinothe ill postino Posts: 10Member
    Thanks --- figured my terminology was off.
  • KC_JonesKC_Jones Posts: 4,128Member
    It's also a merchant coupling, which IMHO shouldn't be there. The more I see them the more I hate them.

    To replace you need to find the actual unions which will allow the pipe to be turned, removed and replaced.

    I do not know what your abilities are, for me that wouldn't be a big deal if it has some kind of access.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    https://www.facebook.com/media/set/?set=a.10202744301871904.1073741828.1330391881&type=1&l=c34ad6ee78
  • the ill postinothe ill postino Posts: 10Member
    edited October 2018
    Ok, so the coupling is attached / detached by rotating the pipe itself, which is why there's no flats for a wrench.
    But then in order to rotate the pipe it has to be freed from a "union", which would have a nut that secures it. Right? I'll have to look up "merchant coupling" but I'm not surprised to hear that it's not the right kind. The main house is sturdy and properly piped but the addition shows signs of lots of weird/bad decisions.
  • HydroNiCKHydroNiCK Posts: 92Member
    If there is no union nearby and you have to cut the pipe anyway....cut the coupling in the pic straight down the center. If your lucky the pipe or pipes will have some play..just enough for you to unscrew each half of the coupling and screw a union back on or a union and close nipple. Then call someone to take a look. Or forget what I just said and call someone to take a look.
  • FredFred Posts: 7,910Member
    Those couplings aren't all bad. It's just that some people don't like them. They are used very frequently on long pipe runs. They don't flats on them because you put a pipe wrench on them just like you would the pipe itself.
  • HydroNiCKHydroNiCK Posts: 92Member
    > @Fred said:
    > Those couplings aren't all bad. It's just that some people don't like them. They are used very frequently on long pipe runs. They don't flats on them because you put a pipe wrench on them just like you would the pipe itself.

    They aren't the same schedule as the pipe they come on...
  • JUGHNEJUGHNE Posts: 5,778Member
    IMO:
    The Merchant comes on one end of 21' lengths of pipe.
    I have used them for decades on gas and hydronic lines.
    After reading the distain about them here, I took a closer look at them. Being steel they will stretch, so reusing one can cause grief....this I know....
    They have no pitch inside. If you put a pencil thru one it lies flat on the bottom. With a proper coupling the pencil will rock in the center because of the pitch/taper.

    Only the taper of the pipe seals them, that is why they often get buried to almost the last thread of the pipes.
    With the proper pitched/tapered coupling you have mating tapers that both tighten up, leaving some pipe threads exposed as with any other fitting.
  • JUGHNEJUGHNE Posts: 5,778Member
    What does the other ends of those pipes have for fittings?
    Pictures.
  • HydroNiCKHydroNiCK Posts: 92Member
    You can get them npt..
  • HydroNiCKHydroNiCK Posts: 92Member
    Better yet..use a dresser coupling.
  • KC_JonesKC_Jones Posts: 4,128Member
    HydroNiCK said:

    You can get them npt..

    Anything 1/8"-2" is straight unless you special order, why special order instead of just buying a normal coupling?

    This topic has been discussed at great length on this and other sites, I think I have hijacked this thread enough.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
    https://www.facebook.com/media/set/?set=a.10202744301871904.1073741828.1330391881&type=1&l=c34ad6ee78
  • JUGHNEJUGHNE Posts: 5,778Member
    Do you have a 1 or 2 pipe rad/system?
    Is this a steam pipe or a return line?
  • HydroNiCKHydroNiCK Posts: 92Member
    > @KC_Jones said:
    > You can get them npt..
    >
    > Anything 1/8"-2" is straight unless you special order, why special order instead of just buying a normal coupling?
    >
    > This topic has been discussed at great length on this and other sites, I think I have hijacked this thread enough.

    I dont know. I dont use those things. Some people are cheap or maybe the smooth cylindrical shape makes them smile...I have no idea. I just stated it can be done since the guy above me seems to be using straight threads instead of npt.
  • JUGHNEJUGHNE Posts: 5,778Member
    edited October 2018
    The Merchant couplings have the straight threads.
    Any pipe threaded or nipple used have the taper, which makes them work (seal) at all.

    The Dresser coupling was mentioned.
    If the OP could saw that coupling exactly in the middle, and hoping for enough swing away of the longer end of the pipe to unscrew the halves of the coupling.
    Then perhaps a Dresser coupling could be slipped over the pipe for reconnection.
    There might be one approved for steam if that is a supply pipe.
    If a return pipe then a standard one might do.
    I would clean the pipe with sandcloth before the sawing.
    Just a suggestion for DIY.
  • the ill postinothe ill postino Posts: 10Member
    JUGHNE said:

    Do you have a 1 or 2 pipe rad/system?
    Is this a steam pipe or a return line?

    1 pipe steam.

    And obviously since I didn't know the difference between a coupling and a union the debate about merchant couplings is above my pay grade!
  • the ill postinothe ill postino Posts: 10Member
    JUGHNE said:

    What does the other ends of those pipes have for fittings?
    Pictures.

    I couldn't see either end --- taking out more insulation should help in one direction but because of how the addition was built the other end is complicated. Need to poke around more tomorrow...

    Also as it was relatively warm today so when i found the leak it wasn't actively leaking. But when I fired up the boiler just to gauge the extent of things it actually seems more like a pinhole leak next to the coupling, rather than the coupling itself. (Or maybe both.)
  • HydroNiCKHydroNiCK Posts: 92Member
    > @JUGHNE said:
    > The Merchant couplings have the straight threads.
    > Any pipe threaded or nipple used have the taper, which makes them work (seal) at all.
    >
    > The Dresser coupling was mentioned.
    > If the OP could saw that coupling exactly in the middle, and hoping for enough swing away of the longer end of the pipe to unscrew the halves of the coupling.
    > Then perhaps a Dresser coupling could be slipped over the pipe for reconnection.
    > There might be one approved for steam if that is a supply pipe.
    > If a return pipe then a standard one might do.
    > I would clean the pipe with sandcloth before the sawing.
    > Just a suggestion for DIY.

    Thats exactly what I just said...😐

    https://www.globalindustrial.com/p/plumbing/fittings/black-malleable/2814412-2-style-90-couplings-for-steam
  • the ill postinothe ill postino Posts: 10Member

    JUGHNE said:

    What does the other ends of those pipes have for fittings?
    Pictures.

    I couldn't see either end ---
    ok to the right I can see another merchant coupling. Still no view in the direction toward the radiator.

    Also, can I link to video? Here's the leak:


  • HydroNiCKHydroNiCK Posts: 92Member
    edited October 2018
    >
    > The Merchant couplings have the straight threads.
    > Any pipe threaded or nipple used have the taper, which makes them work (seal) at all.
    >
    > The Dresser coupling was mentioned.
    > If the OP could saw that coupling exactly in the middle, and hoping for enough swing away of the longer end of the pipe to unscrew the halves of the coupling.
    > Then perhaps a Dresser coupling could be slipped over the pipe for reconnection.
    > There might be one approved for steam if that is a supply pipe.
    > If a return pipe then a standard one might do.
    > I would clean the pipe with sandcloth before the sawing.
    > Just a suggestion for DIY.

    I just exactly said that...😐
  • JUGHNEJUGHNE Posts: 5,778Member
    HydroNick, yes I see that now in your posts...sorry for my lengthy redundancy. :(

    "Yea, she's a steam leaker."
    A dresser might not work unless high temp.

    Might be time to call a steam pro.

    Ill Postino Where are you located?
  • the ill postinothe ill postino Posts: 10Member
    JUGHNE said:

    Where are you located?

    Just north of Boston.
  • FredFred Posts: 7,910Member
    Some great Pros in that area. Go to the "Find a Contractor" tab at the top of this page and put your zip code in.
  • HydroNiCKHydroNiCK Posts: 92Member
    Dresser coupling for steam
  • JUGHNEJUGHNE Posts: 5,778Member
    There you go, just google that.
    You have to know the size of the pipe, if you want this adventure.
    Was the short pipe leaking thru a pinhole.
    You can narrow a leak down by tying a rag around the coupling to keep the water from tracking along the bottom of the pipe,
    high tech method there, but it is effective.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    @KC_jones is correct. Merchant couplings 1/8---2" are straight thread. 2 1/2 and up are tapered. I have used the 2 1/2 and up sizes for years and they are fine.

    I was wondering what size the pipe in the pick is. I am guessing 2 1/2 or larger the way the threads looks
  • JUGHNEJUGHNE Posts: 5,778Member
    OP said this feeds one rad in an addition.
    Nothing there for reference to size.
    To me the threads do not look coarse enough for 2 1/2".
    Ill could measure the circumference of the pipe with a sewing/tailors tape measure around it.
  • the ill postinothe ill postino Posts: 10Member
    JUGHNE said:

    OP said this feeds one rad in an addition.
    Nothing there for reference to size.
    To me the threads do not look coarse enough for 2 1/2".
    Ill could measure the circumference of the pipe with a sewing/tailors tape measure around it.

    I used a clamp to gauge the width of the pipe by tightening it on to the pipe then measuring the gap with a ruler. I get 1.5"
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    So it is a small pipe probably 1 1/4". It would have been better if they had used a malleable coupling with tapered threads instead of a thread protector.

    You might be able to cut through the coupling directly in the middle remove the old pieces and put a union in it's place. As always you have to be prepared if things go bad
  • JUGHNEJUGHNE Posts: 5,778Member
    1 1/4" sch 40 pipe is 1.66" outside diameter.
    The 1 1/4" in the inside diameter. That is what is used in piping terms.
    You did measure the pipe not the coupling?
    Most people can just touch their thumb and forefinger around the 1 1/4" pipe....works for me anyway.
  • unclejohnunclejohn Posts: 1,374Member
    They are there to protect the threads of the pipe and should be thrown away and not used.
  • JUGHNEJUGHNE Posts: 5,778Member
    I agree they are not a good coupling without a taper.
    But if to only protect threads, why not one on the other end also?
    The plastic caps could do that for both ends.

    Anyway, they get used all the time and sometime create problems. They are never going away.
    My lumber yard sells and thread galv pipe for farmers/ranchers,
    all those couplings come off the 21' lengths and go on the shelf for sale at a good price.
  • Keep in mind that there are merchant couplings with reverse threads that the Deadmen used frequently as unions...


    New England SteamWorks
    Service, Installation, & Restoration of Steam Heating Systems
    newenglandsteamworks.com
  • HydroNiCKHydroNiCK Posts: 92Member
    > @New England SteamWorks said:
    > Keep in mind that there are merchant couplings with reverse threads that the Deadmen used frequently as unions...
    So how do you find out? The poor guy is going to cross thread his pipe. The DeadMen probably smoked 3 packs a day too..doesnt mean it was a good idea.
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