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Thread: mixing galvanized and ungalvanized steel pipe

  1. #1

    Default mixing galvanized and ungalvanized steel pipe

    Are there any problems associated with connecting galvanized steel pipe to old black steel pipe, in a forced hot water heating system? I need to connect the old supply and return lines to a new steel radiator/towel-warmer, replacing about 5 ft of pipe. Should the new pipe be galvanized, or should I stay with ungalvanized? Because of the placement of the towel warmer, and the need to zig and zag around around some obstacles, there will be six elbows in that new stretch of pipe, if that makes any difference.
    Thanks

  2. #2
    Master Plumber Dunbar Plumbing's Avatar
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    Default

    Stick with black iron, the material is available and your not mixing up product in your system.

    Local plumbing supply house will have the parts you need.
    Read what the end of this sentence means.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    For your purposes either material is perfectly adequate. Black pipe and fittings are just cheaper. The number of elbows will only be a factor if you have a MonoFlo system.

  4. #4
    General Contractor Carpenter toolaholic's Avatar
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    Default If You mix the two

    Install a 3' brass nipple between the two

  5. #5
    Plumber Cass's Avatar
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    Galvy and black together will be fine.

  6. #6

    Default

    Thanks for the replies. The conflicting opinions make me want to err on the side of caution.

    I searched around the web, and found that dielectric unions and dielectric nipples for galvanized-to-ungalvanized scenarios are sold by mcmaster.com -- and that makes me think somebody must regard that dissimilarity of metals as potential trouble, even if it is not as risky as ferrous-to-copper.

    More than a few people have told me not to worry. The local plumbing supply also told me not to worry .... but who knows, maybe their business depends on plumbing not lasting a long time?

    Anyway, the dielectric nipples and dielectric unions sold by mcmaster.com are not rated for FHW temperatures, according to customer support there. Can anyone recommend another internet supply house?

    Thanks

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Default nipples

    The piping material, not its coating determines whether you need dielectric protection. Galvanized and black pipe are the same material. Heating system historically have been installed with black pipe, but galvanized pipe and fittings are used interchangeably. Domestic water systems are a fresh water system, and for those galvanized is the only steel pipe that can be used, but because of rusting concerns, not electrolysis. The only dielectric device between two steel pipes would either be something made of steel or brass. The supply houses that told you it was okay, gave you the right imformation. They are not interested in selling you another $1.00 part 20 years from now.

  8. #8
    Homeowner geniescience's Avatar
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    Default

    molecules of iron are still iron whether the pipe gets galvanized or not.


    Brass is an unusual metal in that it can be mated to other metals...

    Tim, the fact that someone manufacturers nipples made of brass just confirms this and only this.


    David

  9. #9
    DIY Member northman's Avatar
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    Default anyone know how bronze fits in?

    is it closer to brass or copper? Just curious as I used bronze unions coming off of dielectric nipples, I suspect it is fine, just curious.

    Greg

  10. #10

    Default

    Quote Originally Posted by northman
    is it closer to brass or copper? Just curious as I used bronze unions coming off of dielectric nipples, I suspect it is fine, just curious.

    Greg
    http://www.corrosion-doctors.org/Def...nic-series.htm

  11. #11
    Licensed Grump GrumpyPlumber's Avatar
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    Default

    According to that scale, uranium is the perfect intermediary.
    I'm calling my supplier in the morning, gettin' myself a uranium nipple tray.
    Kidding of course, but it sure is interesting.
    "The biggest regrets we have in life are the chances we never took."

  12. #12

    Default

    I have no long-term experience with any of this, being a newbie DIYer. But I am very skeptical when advice contains the phrase "don't worry about it." It doesn't seem quite natural, not to worry.

    An example: last year, we had to get a new heater, replacing the old one that had been there since WW2 and was originally a coal-burner. The old one was guzzling oil and yet providing no warmth. The warranty from the manufacturer says the warranty is null and void if the sacrificial anode is not checked annually and replaced when necessary. I asked the company who sold it to us and installed it and who does the annual service on it (our heating oil company) about the sacrificial anode when they came to do the annual checkup, and they replied, "Oh, we never bother to check that." I made them check it and note on the receipt that it was OK.

    They probably think I am being a PITA, but I am protecting my $10K+ investment. Like changing the oil on a car. When we go to sell the house, I can tell the new owners that the sacrificial anode was checked annually, and that the heater should give them years of trouble-free heat.

    Regards
    T.

  13. #13
    Rancher
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    Default

    Quote Originally Posted by toolaholic
    Install a 3' brass nipple between the two
    Three Feet?

    Rancher

  14. #14

  15. #15
    Licensed Grump GrumpyPlumber's Avatar
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    Default

    Tim...what name is that boiler?
    "The biggest regrets we have in life are the chances we never took."

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