I'm switching to a tankless water heater and relocating to a new spot. The new spot is right next to the meter, on the inside opposite wall. The main gas line goes into the crawl space (see pic), makes a 45 degree elbow, then a 20ft pipe goes towards all the appliances. I need to put in a tee where the elbow is, and go straight up, then reconnect the 20ft pipe.

From my understanding these are my steps...

  1. Turn gas off at meter
  2. Bleed line, wait 20 min
  3. sawzall 1/2" of pipe out near the elbow (where exactly?)
  4. Undo pipes, remove elbow
  5. Add a tee where the elbow was
  6. Get an appropriate length short piece of pipe and a union fitting to reconnect the 20ft pipe
  7. Plumb in vertical pipe for water heater
  8. Test for leaks

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  • 2
    I think the first step is to make sure you're allowed to do the work. Many areas and companies do not allow DIYers to install/modify gas lines. Check with the local authorities.
    – JACK
    Jul 30, 2022 at 23:01
  • 3
    Uh, you kinda forgot the part where you thread the pipe. This being gas, ain't no push-on couplings here. You need threads. Cutting the pipe with a sawzall means you have two unthreaded ends to deal with and probably no pipe dies. It's also a needless risk of sparks, IMHO. You either need to be able to unscrew things, or you need someone with pipe dies to cut threads. Which I'm guessing might not be you, particularly for a gas job.
    – Ecnerwal
    Jul 30, 2022 at 23:03
  • You also need to be sure your gas supply can handle the amount of gas you'll be using. I believe a tankless hot water heater needs more gas than a standard hot water tank heater, so be sure your supply can provide all you need. This is typically a calculation done by a professional plumber or your gas supplier to determine the capacity of your gas supply.
    – Milwrdfan
    Aug 1, 2022 at 2:08

2 Answers 2


This can be done in some states by the home owner.

Black pipe, gas rated tape or dope usually yellow in color, a union will be needed.

Unions can not be sealed in walls in my jurisdiction.

Last a pressure testing gauge to verify no leaks after the install to a shutoff valve is leak free.

If required permits for the modification.

As others have suggested this is an advanced level DIY if it can be done (you don’t want to blow up your house up).

So check on the regulations and yes it may be possible.

  • This would absolutely require a permit in the jurisdictions I work in. Plus, for the pressure test, the meter would be pulled and everything in the house would be disconnected and capped. (Which often exposes flaws in the rest of the piping, which then need to be dealt with.) So, not really diy in my opinion... Jul 31, 2022 at 3:16
  • 1
    We just turn off each valve and pressure test at the main inlet 15 psi 30 max it has to hold for the time the inspector is there 15 minutes max for the jobs that I did needing a permit. I usually check overnight if possible. No change is a good thing and remember most residential service is only ~3/4 of 1 psi commercial is usually ~2psi
    – Ed Beal
    Jul 31, 2022 at 6:52

Some questions:

Have you ever done this before.

Gas pipes are different than water pipes.

Have you ever made a tread on a pipe ?

If answer is no, call a professional.

Some DIY if you must:

Removing the 45 dgr elbow and replacing with T will not work, still needs 45 elbow.

Cutting the pipe + treading on both sides, now you have the challenge of screwing in both ends. So you will have to loosen the long end all the way to screw it in.


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