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Thread: Dielectric Union Application

  1. #1
    sea-bee chuck b's Avatar
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    Default Dielectric Union Application

    Should I install a dielectric union between the water well source pipe which is galvanized and the new copper which i will install? The entire small cottage is plumbed in glavanized at present. Cannon do much about the galvanized supply linie. Thanks.

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    Moderator & Master Plumber hj's Avatar
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    Your real question should be, "will a dielectric union do any good". Inspectors would require a dielectric for every steel to copper transition. The problem is that a dielectric union is "cosmetic" and looks good for the inspector but does very little to prevent electrolysis. A 6" brass nipple is probably more effective.

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    In the Trades SacCity's Avatar
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    I agree 6" brass nipple is a better way to go.
    The distance between the copper and the Iron is too short in a dielectric union and you end up with a lot of build up right at the joint.
    I've had to replace a number of them to resolve water supply issues.
    Michael
    Last edited by Terry; 04-06-2011 at 09:09 PM.

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    Forum Admin, Expert Plumber Terry's Avatar
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    A third vote for the 6" brass nipple. The City of Bellevue plumbing inspector requires the 6" brass nipple.

  5. #5
    sea-bee chuck b's Avatar
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    Default Further question on 6" Brass Nipple and Dielectric Union.

    A 6" brass nipple? Be patient. Could you explain in detail the assembly please? How is the 6" brass nipple connectetd to the galvanized and the copper at each end? Is it readily available at a Home Depot, or do I need to go to a plumber's supply house?

    Still use a dielectric connector? What method is used at each end to connect to the 6" brass? Do use use a dielectric union at each end as i go from copper to brass to galvanized. Appreciate the advice!




    Quote Originally Posted by hj View Post
    Your real question should be, "will a dielectric union do any good". Inspectors would require a dielectric for every steel to copper transition. The problem is that a dielectric union is "cosmetic" and looks good for the inspector but does very little to prevent electrolysis. A 6" brass nipple is probably more effective.

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    sea-bee chuck b's Avatar
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    Hi Terry,

    what a good chance to thank you for this great site. so helpful. would this wisdom also apply to a water heater connection and be helpful in reducing buildup? Again, thanks...this is such a great enjoyable site. jsut bought this wonderful cottage (650 sq. ft.) on a nice lake just south of the Mackinaw bridge in northern michigan. doing a lot myself to save $$$. this is so valuable. chuck b

  7. #7
    Test, Don't Guess! cacher_chick's Avatar
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    A female fitting is installed on the ends of both the galvanized and the copper pipe, and the 6" threaded brass nipple connects the two together. Threaded brass nipples are available at any reputable hardware/plumbing store. This IS a dielectric, and accomplishes the same thing as a dielectric union, only better.

  8. #8
    sea-bee chuck b's Avatar
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    Just want to be sure...you are suggesting a female fitting made of copper for the copper supply line to the cabin end, and a GALVANIZED femail fitting at the water well galvanized end, sith the 6" brass nipple in between as a sort of elongated dielectric union? Have noticed that the dielectric unions that i have installed on a water heater, have a plastic liner in them...is that a problem not being in the brass nipple? also, would this arrangement also be a better connection for a water heater as well?

  9. #9
    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by cacher_chick View Post
    A female fitting is installed on the ends of both the galvanized and the copper pipe, and the 6" threaded brass nipple connects the two together. Threaded brass nipples are available at any reputable hardware/plumbing store. This IS a dielectric, and accomplishes the same thing as a dielectric union, only better.
    Pretty sure you'd need a union somewhere...

  10. #10
    One who lurks Basement_Lurker's Avatar
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    Quote Originally Posted by chuck b View Post
    Have noticed that the dielectric unions that i have installed on a water heater, have a plastic liner in them...is that a problem not being in the brass nipple? also, would this arrangement also be a better connection for a water heater as well?
    Only the real cheapo water heaters don't come with unions factory installed. Any reputable brand will supply factory installed galv nipples which are lined with plastic...that's what you want. If you don't have those, then brass ones are a good substitute. You can adapt however you want from that point...be it hard piping with copper, or using one of the many variations of flex connectors.
    Broken promises don't upset me. I just think, why did they believe me? -Jack Handy


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    Moderator & Master Plumber hj's Avatar
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    quote; Only the real cheapo water heaters don't come with unions factory installed. Any reputable brand will supply factory installed galv nipples which are lined with plastic...

    1. I have NEVER seen a water heater with unions factory installed.
    2. Apparently you have never seen "dielectric nipples" which have delaminated with rust between the plastic and steel..
    3. the idea is to get separation between the two disimilar metals by using a material which is between them in the Noblility scale. Brass is that material when it comes to steel and copper.

    Last edited by Terry; 04-12-2011 at 08:22 PM.

  12. #12
    One who lurks Basement_Lurker's Avatar
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    1. Whoops, by factory installed unions, I meant factory installed nipples.
    2. You are correct, I have never seen laminated nipples suffer from that much corrosion.
    3. I use dielectric flex hoses to make my transitions, however otherwise I use cast brass FIP adapters or tank tees when hard piping with copper, I'm sorry I wasn't more specific for your liking, heh.

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  13. #13
    Moderator & Master Plumber hj's Avatar
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    quote; I'm sorry I wasn't more specific for your liking, heh. (whoohooo lucky post #666)

    It was not to MY liking because I didn't want someone who did NOT know what you meant to get the wrong idea. And I also use dielectric flexs, but that is NOT what the original question was about.

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