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Thread: do I need to use a dielectric nipple

  1. #1

    Default do I need to use a dielectric nipple

    I have just installed a AO smith gas water heater. All my water lines are 3/4 inch copper. The Tank came with 2 dielectric close nipples with no mention in the installation instructions.

    My old tank of 15 years had the copper 3/4 male fitting screwed directly into the top of the tank with no problems.

    Question : Should I now use the nipples directly into the top of the new tank and then get a female copper fitting to screw directly onto the nipples or should I just thread the male copper fitting into the tank like it was in the previous install and throw the nipples away?

    A web search shows installs both ways.

  2. #2
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    Use the nipples. If they were not important, they would not have been included.

  3. #3

    Red face Keep the nipples

    OK, thanks

  4. #4
    DIY Senior Member Mike Swearingen's Avatar
    Join Date
    Jan 2005
    On Albemarle Sound In Northeastern NC


    Absolutely, as Gary said.
    Di-electric nipples are to prevent rapid electrolysis corrosion from galvanic action between two dissimilar metals (steel water heater tank and copper or brass connections), the first place that you'll have a leak if you don't.
    Use 3-4 flat wraps of teflon tape wrapped clockwise only as the threaded end of the nipple faces you on both ends before installing.
    I use the flex copper-with-brass fittings water heater connectors on the di-electric nipples to the supply and outgoing hot water pipes.
    Good luck!

  5. #5

    Thumbs up Thank you

    It seems to be an interesting subject. A search on the web shows a split between the people that use them and the people that don't. A local plumber in my area says he does not bother with the nipples. He says his experience has shown that the tank goes bad before the fitting leaks. I mean the tank I replaced was 18 years old and had the copper fittings installed directly into the top of the tank.

    The nipples are galvanized and there is still some exposure of steel to galvanized to copper because the plastic insert does no cover the metal 100% on the ends, but I guess it is better than full exposure.

    Thank you for taking the time to respond and I'll probably pull mine apart and do it right based on your suggestions.


  6. #6
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    The point of a dielectric nipple is that the electrolyte (water) never touches the electrode ( galv) hence no current can be induced. Yes the copper or brass touches the galv, but the plastic lining prevents the water from creating a complete path for current flow.


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