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Cutting a existing steam pipe and rethreading it

Hi All,

Is this done often? I have an old line that was capped years ago. I would like to reuse it but need to shorten it and rerun new pipe to the radiator.

Wasn't sure if I would be able to just cut it cleanly and rethread in place.

Thanks in advance.


  • RobG
    RobG Member Posts: 1,850
    Sure, just make certain that it is secure so that you don't damage any of the existing piping. Depending on the size, I prefer to do it with a hand threader so that I can control the torque on the pipe.
  • jjstokes
    jjstokes Member Posts: 2
    Thanks RobG.

    For cutting the pipe, could I use a sawzall or will that not be a clean/square enough cut?

    Pipe size is 1 1/4".
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    I usually run a pipe cutter around a few times to score the pipe, then use that score as a guide and finish cutting with a hacksaw. I find the reciprocating saw hard to work with if the pipe is in an awkward position--they always are--and if the blade binds it jerks the pipe sideways and I'm lucky if it doesn't cause a leak somewhere.

    Threading in place is risky, because you can drive the other end of the pipe farther into its fitting, and that can create a leak. If you can, stabilize the pipe with a pipe wrench or chain wrench clamped to a large, immovable object, and use plenty of light threading oil (not the dark kind you use with power threaders).
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • icesailor
    icesailor Member Posts: 7,265
    Cutting off with a Sawzall usually leaves you with a pipe cut off on an angle.

    I always used my Ridgid single wheel cutter to cut a groove as much as I could. Then, switched to my Ridgid 4 wheel cutter. I got the most accurate and straight cuts that way. Some hardware stores rent tools. One near where I used to live had them. I owned my own.

    Cutting it off and trying to thread it after is living life on the edge. If you're really in a jam cutter wise, if you have the room, make a wooden miter box, the same width as the pipe. Cut as perfect a 90 degree cut in it as you can. Set the box on the pipe however you best can (duct Take etc) and cut the pipe, using the Miter cut in the box as a guide. If it is the slightest bit crooked, you will have to be really careful starting the die.