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Thread: Nipple with cocked threads?

  1. #1
    DIY Junior Member RobertM's Avatar
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    Default Nipple with cocked threads?

    Take a look at this photo. Follow the pipe down from the top and you can make out how the lower pipe is "cocked" a bit to the side after the union. I thought maybe it was the union or how I put it together and changed it to a coupling, since I did not like having a union that could get undone on a gas line anyway. The pipe needs to get out of the way to move the water heater. Well, after changing to a coupling, the pipe is still cocked to one side. The only thing I can think of is that the threads are not concentric to the centerline of the nipple and causing the misalignment. I have never seen this before, can someone explain? The pipe sealed up just fine and it tightened up normally during installation. Looks a bit crappy, but probably just cosmetic?
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  2. #2
    In the Trades Gary Swart's Avatar
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    I see what you mean, but it may be the pipe has as slight bend which give the illusion of a cross thread. Have you tested the joint for a gas leak? If it doesn't leak, I'd say you're good to go. Use undiluted dish detergent and swab the connection. Look for bubbles. No bubbles=no leak.

  3. #3
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    If the pipe was just bent you would of noticed quite easily while tightening up the pipe, if the threads didn't cross thread.

    With the pipe being bent that much it would wobble quite a bit while it was being tightened up.

    I would take the piping apart and inspect it further just to make sure you didn't cross thread anything.

  4. #4
    DIY Junior Member RobertM's Avatar
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    I inspected all the pipe I used thoroughly prior to purchase, you have to do that when you buy the crap HD sells. Most threads looked rough, some pipes looked to have been prior installed and returned, some were clearly out of round, others just plain damaged. I picked the best of the lot, which isn't saying much. I ended up throwing away the smaller nipples and going with brass due to the piss poor quality after finding some oval shaped ones that actually screwed in nicely, but probably would not have held. Some did not even look schedule 40.

    I then visually inspected all threads, cleaning them with a brass brush and picking out the occasional crud, some of it quite hard and probably would have affected tightening. I chucked all pipe, screwed hand tight, made a mark, then used two pipe wrenches to go at least one full turn, sometimes a bit more. All piping was tested using Rector Seal's gas leak testing product, which is excellent, way better than the soapy sprays I'd used in the past. The stuff is thick and stays on the joint. The only leaks I had were at unions. The long pipe is the most suspect. I eyeballed it and before reinstalling and it looked straight. The threads were fine. I guess eyeballing is not a good enough approach.

  5. #5
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by RobertM View Post
    I inspected all the pipe I used thoroughly prior to purchase, you have to do that when you buy the crap HD sells. Most threads looked rough, some pipes looked to have been prior installed and returned, some were clearly out of round, others just plain damaged. I picked the best of the lot, which isn't saying much. I ended up throwing away the smaller nipples and going with brass due to the piss poor quality after finding some oval shaped ones that actually screwed in nicely, but probably would not have held. Some did not even look schedule 40.

    I then visually inspected all threads, cleaning them with a brass brush and picking out the occasional crud, some of it quite hard and probably would have affected tightening. I chucked all pipe, screwed hand tight, made a mark, then used two pipe wrenches to go at least one full turn, sometimes a bit more. All piping was tested using Rector Seal's gas leak testing product, which is excellent, way better than the soapy sprays I'd used in the past. The stuff is thick and stays on the joint. The only leaks I had were at unions. The long pipe is the most suspect. I eyeballed it and before reinstalling and it looked straight. The threads were fine. I guess eyeballing is not a good enough approach.
    You may want to check with your local area but in most places brass is not allowed for gas piping because it's porous.

  6. #6
    DIY Senior Member kreemoweet's Avatar
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    "Porous" brass pipe? I don't think so! Brass pipe and fittings are specifically approved for gas systems in the Uniform Plumbing Code.
    Brass pipe and fittings have been successfully used in gas systems for well over a century!

  7. #7
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    We use brass fittings basically when using copper. But the first code clause in the BC gas code book for piping and materials:

    6.1.1
    A gas piping or tubing system shall be of steel, copper, or plastic.

    And even when you use brass for flared connections you must used forged brass nuts not machine brass nuts.

    But you certainly can't use brass nipples to connect your gas work togeather.

    But ofcourse our codes differ quite a bit!

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