In my crawl space I have a fairly convoluted maze of black iron gas connections which only serves 2 appliances. During basement renovation this maze gets in the way and I would like to remove most of those connections and replace with as direct as possible lines to my appliances. I, however, don't want to take apart the wall to replace pipe all the way to the outlet. So I will inevitable end up with something like two male threaded pipe ends that need to be linked with each other.

Is there a good, code-compliant way to connect those sections of black iron pipe houseline? Something like flared connection would work, perhaps, but I can't find anything suitable for iron pipe.

  • are you legally allowed to work on gas line?
    – jsotola
    Commented Nov 28, 2020 at 1:18

3 Answers 3


You need a left-right coupling/nipple set, available at any plumbing shop and legal to use in that application (but check with your AHJ to make sure).

As mentioned elsewhere, a traditional pipe union is generally not acceptable anywhere within the envelope of the foundation of the home.


Replace the whole lot with CSST.

Cut out piping in the middle, disassemble back to convenient locations, and re-connect using corrugated stainless steel tubing rather than hard black iron pipe. Sure, the CSST costs more, but routing it out of the way of your renovations will be much easier. Best of all: because the connectors spin freely you can easily join it up to the existing black pipes at both ends without special tools or obscure fittings.

  • There are kits out there that will supply everything needed to convert over from black pipe. There is a conversion part needed, but it is included. The price didn't appear to be that bad, considering the alternative of cutting and threading black pipe, aside from using a union inside a house which is a bad idea to me, especially if it is not to code....
    – Jack
    Commented Nov 28, 2020 at 19:25
  • Thanks. I was thinking CSST as well. Just was not sure if it's allowed to be inserted anywhere and if it requires special licensing (most instructions state that one is supposed to be authorized to work with it.)
    – Uncle Meat
    Commented Nov 29, 2020 at 0:23
  • @UncleMeat You'll have to check with your local authority and with the manufacturer. There could be restrictions on use or required techniques for passing the pipe through floors etc. I don't recall hearing of building authorities requiring special licensing for CSST installers, but I do recall that some manufacturers only wanted to sell their product to trained installers through official dealers. Now there are CSST options offered in home centers.
    – Greg Hill
    Commented Nov 29, 2020 at 4:15

A standard pipe coupling would be the proper thing to join 2 pipes in a wall. Some may suggest a Union but in my jurisdiction they are not allowed inside concealed spaces. Use of gas rated pipe dope or PFTE tape is required some is yellow in color but not all.

  • I don't think I can rotate male pipes. And if I rotate coupling wouldn't it tighten one side while loosening the other?
    – Uncle Meat
    Commented Nov 28, 2020 at 1:19
  • Doing more research, it seems that it will need left-right coupling and niple.
    – Uncle Meat
    Commented Nov 28, 2020 at 1:47
  • Do you have a left handed dye for a threader? This is the only way I know to do left right couplings the r12 ratchet handle and left hand dye can cost 150+ I I think my left handed dies were ~100$ ea I already had both a hand ratchet and power threader and I rarely ever use them I start at 1 end and work to the other, if the remodel has the walls open the extra work and cost is really not worth the cost if the walls are not open and you have limited access then left right is an option.
    – Ed Beal
    Commented Nov 28, 2020 at 2:21
  • Looks like left-right couplings and niples are available for purchase. Hopefully, it will be sufficient for my project.
    – Uncle Meat
    Commented Nov 28, 2020 at 2:45

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