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Thread: black pipe assembly technique

  1. #1

    Default black pipe assembly technique

    I am helping my plumber do some of the work on my house, under his supervision
    and I'm good with PEX and copper, but can't seem to get the hang of black iron
    using Gasoila on first 3 threads, not too much, well-seated into threads, and tightening 'not too tight' (my plumber's instruction)
    but I think his idea of not too tight and mine are quite different
    redid some of the boiler trim and on pressurizing (only 15 psi) had drips at most of the unions
    so I am thinking I need to go WAY tighter
    maybe he means not gorilla tight
    the only tip I've found online is 'hand-tight and then 1.5 extra turns w/ a wrench'
    which is pretty close to what I was already doing
    (maybe not quite 1.5)
    but how do you go 'hand-tight' with a short nipple, for example? if one thread catches slightly, you're 'hand-tight' but not anywhere near 'sealed'
    I'd raher have torque recommendations for 1/2", 3/4", 1" etc
    or some other benchmark for how fully to apply the wrench

    and what is the danger of going 'too tight', anyway?

    anyone have any other rules of thumb?
    thanks very much
    Last edited by rbptlp; 05-23-2007 at 08:36 AM.

  2. #2
    Plumber jimbo's Avatar
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    Hand tight + one wrench turn is a rule for plastic pipe. It is not tight enough for black pipe. The link below shows the thread engagement , hand turns + wrench turns for various sizes of pipe. What size are you using? And you mentioned unions.....is it the union joint that is leaking, or the threaded pipe connection to the union fitting.?

    http://www.sizes.com/materls/pipeThrd.htm

  3. #3
    Master Plumber Dunbar Plumbing's Avatar
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    Gas is not water. Gas kills and having a gas leak on a gas line you just touched will scare the hell out of your customer whether it is a seepage leak or not. You'll lose that customer forever as well because they'll think you endangered thier life.

    I crank them till they stop. You can always tell if black iron was threaded by a new or old die. Old die usually means the pipe is going to travel all the way to the end. Newer will have that connection 3 to 4 threads deep.

    I take no chances on black iron because I know those systems over years start to leak from all the vibrations of the structure, causing the threads to allow leaks. I get calls from the utility company from customers stating the gas was just shut off and they found 13-20 leaks in the gas lines.

    Get there and the piping looks like the day it was installed.
    Read what the end of this sentence means.

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    if you depend on hand tight with any specific number of turns with a wrench, you WILL have leaks. Properly adjusted sharp dies cut proper threads, but if they are not adjusted correctly they will either cut tight or loose theads and your "rule" will no longer work, even it it ever did. Old dies cut tighter threads because they are getting worn, so those will need more tightening that newer ones.

  5. #5

    Default update

    thanks for the tips
    according to the chart, 4.5 hand turns + 3 wrench turns is standard for both 1/2" and 3/4" black pipe
    that is probably more than I was doing, and may have been more than I am capable of doing
    I will count next time (I might have been doing more hand turns than I think)
    reassembled boiler trim yesterday going considerably tighter
    I also used a combination of teflon tape and Gasoila soft-set sealant (talked to Gasoila and that is what they recommended for problem joints)

    I think part of the problem is that my plumber put together the trim with a mix and match of what came with the boiler, his own odds and ends, and new stuff from the supply house
    so unlikely that any two pair of threads was matching up perfectly

    but it sounds like you are all pretty much saying go as tight as you can, that there is danger going too loose, but not a danger going too tight
    why did my guy say 'not too tight' ??

    again, thanks for the help

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    It's a tapered thread. In theory, if you tighten too much, it is like putting a splitting wedge into a log; you could split the fitting. Really hard to do, but possible.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7
    Plumber jimbo's Avatar
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    I should have also mentioned to read the note that accompanies that thread chart I linked to. They ackowledged that field cut threads, and often even factory cut threads, do not have the full length of threads called out, and hence the variation in the turns required for "tight". I think we are all in agreement that you probably did not get it tight enough, because 3/4" pipe with for example a 12" wrench would take considerable effort to get tight. Unless you have arms like Mighty Joe Young an 18" wrench would not be too big!

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default tight



    I use a 10" wrench on 3/4". An 18" wrench is WAY, WAY too big, unless you are a 98# weakling and need the Charles Atlas body building set. Do not spend any time following a chart as to "generic" threads. Just use some common sense. My wife's uncles put the waterers in for a dairy barn once. Since it was modular they precut the system, using the standard calculation for make up. Then they went in for dinner while the farmer's sons put the pipes together. Since the sons were built like 600# gorillas they tightened the pipes until there were no threads showing. By the time they reached the last waterer, the openings were 3" short from where they should be. The entire thing had to be taken apart and new fittings used because the old ones had been stretched by the tightening.
    Last edited by Terry; 08-01-2007 at 02:12 PM.

  9. #9
    DIY Junior Member
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    For a correct pipe thread you should be able to hand tight the fitting 3 turns, use a anaerobic pipe sealant on thread first then 4 turns with tefon tape, hand tight fitting on to pipe, wrench tight fitting 1.5 to 2 times with 14" wrench for pipe sizes 1/2" to 1" you will never get a leak, for union smear a coat of anaerobic sealent on union face, 2 to 3 turns of teflon tape on union thread tighten with 2 x 14" wrenches, 1 to tight 1 to hold against, make sure union faces butt up square, force tight but dont kill it.

    Clive

  10. #10
    Master Plumber master plumber mark's Avatar
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    Talking grease it up and crank it down

    I have run into many gas lines that were
    literally only hand tight with the "tefflon slick tight"
    on the threads.....

    it works , but its not right and is sort of scarey to me..

    I ran into a drip leg on a water heater last year that
    literally fell out in my hand when I began to loosen it.
    the fellow must have jsut put it in there one or two turns
    and it vibrated itself outover the years.....


    Put tefflon tape on the pipe if you so wish...then
    Put pipe dope LIBERALLY on the male threads. just
    slop it on heavy , the dope is cheap and is less expensive than a leak......

    then tighten down the pipe till it feels "taught"


    not breaking the pipe off in the fitting , so the next poor bastard
    that comes along cant ever get the pipe apart again... and not "sissy" hand tight either ..


    "taught" is a point of tightness
    you learn from simply from doing it.
    Last edited by master plumber mark; 05-27-2007 at 05:55 AM.

  11. #11
    Master Plumber Dunbar Plumbing's Avatar
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    Anyone know where you can find that coated underground pipe? Black iron that is that has the protective coating.
    Read what the end of this sentence means.

  12. #12
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    If you really want it, I personally will only use it for very short underground runs, most plumbing supply stores will have it. The only way I will use it is if I wrap the ENTIRE pipe and fittings with the protective tape, not just the fittings and damaged areas. It is about the worst material you can use, other than unprotected pipe. It would be better if it were at least galvanized pipe with the coating.

  13. #13
    DIY Junior Member
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    I agree, I would not use it as a lead in water supply, either type k copper or cpvc pipe, cost wise cpvc is the best for your buck, I just installed a 80ft lead in 2" glued fittings, piping will run 160 psi in service we tested to 200 psi for 2 hrs no problems, has some issues with back fill and compacting but is clean, approved for potable water, and has a great C-factor.

    Clive

  14. #14

    Default thanks all

    I have re-done both the boiler trim and the gas line and both are now 'taught' (I like that term, and I feel it now) and completely leak-free
    thanks again for all the feedback

    (my rule of thumb now is 2 turns Teflon + Gasoila first 3-4 threads, roughly 7 turns total - usually about 4 turns hand tight and 3 more with a 14" wrench - I adjust as needed - some threads want another full turn, or even 2; some need a little less
    but now I know what tight feels like)

  15. #15
    DIY Member gtmtnbiker's Avatar
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    Default

    I have some questions on black pipe assembly.

    What do you do if you're trying to put a T on the pipe and it needs to be aligned in a certain direction?

    So if I put the fitting on hand-tite and then use a pair of wrenches (one to hold mating pipe) to tighten it, I want to ensure that it's tight but I don't want to over-tighten. Also, it has to line up in some direction.

    There were several posts that reference the word "taught". I think they meant to say "taut", right?

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