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Thread: Rigid conduit

  1. #11
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    Jan 2008
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    NC & IN
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    The best part about plumbing pipe is that you can get it on 20 ft lenths

  2. #12
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    Dec 2012
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    Placerville, CA, USA
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    Quote Originally Posted by OldSparks View Post
    In addition to what JRaef posted, I was taught that the threads on pipe are slightly tapered, where the threads on conduit are not. (Tapered in the sense of the die that cuts the pipe threads is slightly larger in diameter at the leading side of the die.)
    Actually, the threads on rigid (pipe) are (or should be) tapered just as for plumbing pipe. Female threads on Bell boxes are also tapered. But the male threads on most connectors and the female threads on couplings may not be. It is puzzling. For plumbing pipe tapered threads are necessary to make a water or gas tight connection. For electrical use we often do not care.

    Sent from my XT1585 using Tapatalk

  3. #13
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    Feb 2003
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    Illinois
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    Quote Originally Posted by Buck Parrish View Post
    The best part about plumbing pipe is that you can get it on 20 ft lenths
    Conduit is available in 20' lengths and is often used on long industrial conduit rack installations.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

  4. #14
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    Feb 2003
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    Illinois
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    Quote Originally Posted by GoldDigger View Post
    Actually, the threads on rigid (pipe) are (or should be) tapered just as for plumbing pipe. Female threads on Bell boxes are also tapered. But the male threads on most connectors and the female threads on couplings may not be. It is puzzling. For plumbing pipe tapered threads are necessary to make a water or gas tight connection. For electrical use we often do not care.

    Sent from my XT1585 using Tapatalk
    Not sure if the conduit couplings ever had taper threads in the USA, but in Canada, they did until the early eighties.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

  5. #15
    Join Date
    May 2013
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    Massachusetts
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    2,395
    Quote Originally Posted by nizak View Post
    What is the difference between the Galvanized Rigid steel pipe located in the plumbing section and the GRMC sold in the electrical department?

    Threads seem to accept a coupling the same but difference in cost is $16.

    Thanks
    In any case, you are not allowed to use them in each others' applications. Plumbing pipe doesn't carry a UL listing like conduit does, plus it has the interior seam that is a source of abrasion for wire pulling. Conduit is made from an alloy of steel that is intentionally weaker than that of plumbing pipe (in order to be able to field-bend it), so it will not carry the same pressure rating. Both pipes have the same taper/thread dimensions on the male threads, but conduit couplings have straight female threads, and will also not allow a watertight seal to the same pressure rating as tapered-in-tapered connections used in plumbing.

    You can use them interchangeably in an application unrelated to plumbing or electrical (like a post for mounting equipment), provided that either will be strong enough for the application, but to use them in either plumbing or electrical work, you have to use the product built for the purpose.

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