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What Threads are these? Radiator Water Supply Lines.

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HandyFS
HandyFS Member Posts: 108
edited October 2022 in THE MAIN WALL

I have a radiator that I need to remove and I want to temporarily patch a loop into the line so the piping can work as intended with the flow of water. What are common thread ends on radiator valve and radiator ends? I tried an NPT end and it fit on one end, but not the other. I also tried what I think is a FIP adapter but it didn't seem to work. Are MIP and FIP threads typically used for old cast iron radiator connections where they connect onto a union or valve? These are brass (Not Iron/Steel), but they seem to possibly be MIP/FIP or something else.

Can anyone confirm? I want to get a female end on and get this temporarily looped or capped. Any tips appreciated.

Comments

  • pedmec
    pedmec Member Posts: 994
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    That's a ground joint union thread. its not pipe size at all. not ips or npt. the seal is the face of the two mating surfaces
    mvickers
  • ScottSecor
    ScottSecor Member Posts: 863
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    Most likely proprietary. In other words not readily available. I have tried using two different brands of unions many times (for radiators and pipes). I don't think I was ever successful and stopped doing it soon after I entered the heating business. If you have the other half of the union you may be ok, if not replace the entire fitting.
    mvickers
  • HandyFS
    HandyFS Member Posts: 108
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    pedmec said:

    That's a ground joint union thread. its not pipe size at all. not ips or npt. the seal is the face of the two mating surfaces

    That makes sense. Oddly one side fits a 3/4" adapter I have fine, the other one is an oddball size.

    Most likely proprietary. In other words not readily available. I have tried using two different brands of unions many times (for radiators and pipes). I don't think I was ever successful and stopped doing it soon after I entered the heating business. If you have the other half of the union you may be ok, if not replace the entire fitting.

    Thanks for the knowledge and experience, at least I know to not go crazy trying to find it then. I'll cut it out and get my own ends on temporarily and then when a radiator goes back in place I'll mate it with new ends. Thanks.
  • pedmec
    pedmec Member Posts: 994
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    It fits the tailpiece that is in the radiator. It matches that tailpiece. It won't match another manufacturer.
  • HandyFS
    HandyFS Member Posts: 108
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    pedmec said:

    It fits the tailpiece that is in the radiator. It matches that tailpiece. It won't match another manufacturer.

    That makes sense. I'm going to cut it out and rework the parts between the water line and that old mated pair.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,153
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    As you have already discovered the exposed male thread is part of the union that is still in the radiator that was removed.

    The pipe coming from below the floor will have a standard male pipe thread. There are black and galvanized pipe thread caps that will fit nicely there.


    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • HandyFS
    HandyFS Member Posts: 108
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    As you have already discovered the exposed male thread is part of the union that is still in the radiator that was removed.

    The pipe coming from below the floor will have a standard male pipe thread. There are black and galvanized pipe thread caps that will fit nicely there.


    Thanks Edward, that is super helpful and a good reminder to go for those basic threads where I can. Some of the lines are straight copper, others are threaded so I'll cut if needed, or unthread the union as you suggested. I was just trying to save myself some extra work redoing the connections, but with non-standard threads I guess I have no choice. Thanks again.

  • mvickers
    mvickers Member Posts: 30
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    You may want to unthread vs cutting it out and save it to reuse the radiator
    PC7060
  • jpcallan
    jpcallan Member Posts: 15
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    Can you measure the O.D. and threads per inch?
    There is a U.S. thread standard called NPSM or National Pipe Straight Mechanical that might match, although I agree with all of the prior responders that this is a part of ground union joint.