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Fittings for Gas service ???

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heathead
heathead Member Posts: 234
I have a really simple question. The steel female fittings / couplers that come on 21 sticks of schedule 40 steel pipe, can those be used they don't seem to be marked. I had always though one could, no way an inspector would fail new gas service if their are no marking on the fittings? Service is in NJ at moms house. I would think those would be stronger that the cast couplers.

Thank you.

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  • Alan Muller
    Alan Muller Member Posts: 31
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    The steel couplings on "T&C" pipe are usually threaded straight through rather than having properly tapered pipe thread. Are they more likely to leak? Good question.
  • realliveplumber
    realliveplumber Member Posts: 354
    edited March 2022
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    They are called merchant couplings. They are required to be welded to the pipe after they are threaded on. They are tapered threads.
  • Alan Muller
    Alan Muller Member Posts: 31
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    Here is a brief discussion of different types of merchant couplings: https://blog.boshart.com/the-different-types-of-merchant-couplings
    JUGHNE
  • JUGHNE
    JUGHNE Member Posts: 11,095
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    If tapered why then is welding required?
    One does not weld tees or 90's.

    The Merchant couplings I see are not tapered.
    Take one and lay a straight pencil inside against the threads.
    Straight across.
    Try the same with a "proper" coupling and you see the taper.

    That being said, I have used them on low pressure gas and steam.
    They tighten only with the taper that is on the pipe or nipple.

    Matching taper on fitting and pipe will make a better seal.
    IMO

    I would spring for the cast couplings for the job...you never know what an inspector had for breakfast that morning.....or the night before. ;)
    Larry WeingartenEdTheHeaterMan
  • realliveplumber
    realliveplumber Member Posts: 354
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    Sorry, meant to say that they are tapered threads over 2"
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,767
    edited March 2022
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    Those merchant couplings including 2'" and smaller cannot be used on gas they have straight threads. Some call them thread protectors.

    2 1/2" and up they have a tapered thread and can be used


    I did a job with 500' of 3" threaded gas pipe. It was low pressure gas in a mill with a lot of dust all over the place. There was NO way to weld this without burning the place down.

    500' is 23 3" couplings

    I wasn't going to buy 23 malleable couplings I didn't need and throw 23 steel ones away. That's probably $350 now, so I used the steel ones that came with the pipe. I could have bought plain end pipe but why spend all that time cutting 46 extra 3" threads?

    I had the documentation that showed they were a tapered thread.

    The inspector didn't want to pass it so I said that's fine

    We will take it to the plumbing board in Boston because I am not taking all this apart and we can let them make the decision. He made the phone call to Boston.

    It passed.

    He was my best buddy after that I never had any more problems in his town
    JUGHNEwmgeorgemattmia2
  • heathead
    heathead Member Posts: 234
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    Thank you all learned something new. Going to use the proper coupling.
  • JUGHNE
    JUGHNE Member Posts: 11,095
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    Good choice for your project, probably not much extra expense, considering the possibility of rejection......that wouldn't impress mom.

    I do not use them on gas anymore after reading similar past discussions such as this one.

    Some people say they throw them away.
    I don't, I will use them on some steam condensate or something with about no pressure.
    Our lumberyard/hardware store that sells and threads pipe will put those couplings on the shelf to sell at a hefty price. People just tighten the hell out of them.
  • Henry
    Henry Member Posts: 998
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    I have not checked my NFPA54 but it should be consistent with our CSA B149.1 says that 2 1/2 inch and larger pipe must be welded.
  • Intplm.
    Intplm. Member Posts: 2,041
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    I have seen the "thread protectors" used very often.

    But I had one guy do a job in a warehouse. The gas pipe was installed forty feet in the air.
    The building inspector made him rip it all out and install couplings with ribs on them.
    The inspector said that is how you identify a true coupling from a thread protector.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,767
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    Read the attached. 2" and smaller straight tapped 2 1/2 and up taper tapped. No reason not to use the taper tapped ones in the larger sizes.

    It is quite common for those that know welded pipe that when they fabricate tanks, boiler feed tanks, steel boilers etc. and they have to put tapings in those what do you think they use????? They don't use weld o lets all the time


    They are not welding in malleable couplings with the ribs on them. Those are malleable iron, not steel. They are welding in steel couplings, either full or half couplings just like the ones shown on the attached sheet. And we thread pipe into those connections, don't we?

    Inspectors don't know everything, you have to know more than they do and educate them. You don't argue with them (they have the badge and the gun LOL)

    But if you show them you know something they become your friend and leave you alone
    Intplm.
  • heathead
    heathead Member Posts: 234
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    I did take a saws all to one of the fittings and made a slot just thick enough to place end of tape measure in, then duct tape to keep it there. Screw the fitting on the pipe, place end of tape measure in slot then pull across room for accurate cut lengths. Makes measuring pipe with one person really easy. I will post pictures later when I go back to finish the job.
  • mattmia2
    mattmia2 Member Posts: 9,850
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    There is a rule of thumb per pipe size for the amount that will thread in to the fitting, you can just add it to the measurement between fittings.