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Thread: Dielectric unions and water heaters

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    General Contractor dx's Avatar
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    Default Dielectric unions and water heaters

    Two related questions:

    1. We are installing a Bradford White heater for a customer. Looking at their installation manual, they have a picture showing the connections to the nipples, then elbows and short horizontal pieces of pipe, then unions (for both hot and cold). Note that the unions are NOT at the nipples of the heater. And no mention anywhere of dielectric unions. The nipples on the heater look like normal plated steel nipples. Have they found a way to eliminate the need for dielectric unions, or is the installation picture/instructions wrong? I will call them on Monday, but just curious if anyone has seen this before.

    2. As I was buying the dielectric unions for the above job, I noticed that a sharkbite to 3/4" FPT is actually cheaper than the 3/4" dielectric by about 50 cents. Not to mention a lot quicker to install. Can this be used as a dielectric union between steel and copper? The body is brass, and as far as I know brass to steel is fine. And brass to copper also fine.

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    sharkbites are nice but theyre still plastic guts and you should have 18"-24" of copper(metal) before you transition to any form of plastic

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    Plumber Cass's Avatar
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    Sharkbites are brass not plastic...and will work better than dielectric unions as they won't rust shut...

    What do you mean "1. We are installing a Bradford White heater for a customer." who is we...
    Last edited by Cass; 12-19-2009 at 04:13 AM.

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    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    Quote Originally Posted by Cass View Post
    Sharkbites are brass not plastic...and will work better than dielectric unions as they won't rust shut...

    What do you mean "1. We are installing a Bradford White heater for a customer." who is we...
    They also make a fitting similar to sharkbites that is plastic. It is also approved for hot water. I wouldn't use them. I don't like snap click plumbing.


    John

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    Moderator & Master Plumber hj's Avatar
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    Default dielectric

    The dielectric is brass, but the length of the brass component is also important because elecltrolysis takes place through the water, not the metal so the further the steel and copper are separated the better. We use a 6" brass nipple, but the Sharkbite would only create a 1/2" separation which would be ineffective.

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    General Contractor dx's Avatar
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    Quote Originally Posted by hj View Post
    but the Sharkbite would only create a 1/2" separation which would be ineffective.
    Looks to me like a lot more separation than a regular dielectric union. The sharkbite is all brass. The regular dielectric has the steel and copper right next to each other.

    I am sure there are many ways of creating better separation, I'm only asking sharkbite vs. regular steel/brass dielectric union.
    Last edited by dx; 12-19-2009 at 07:26 AM.

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    General Contractor dx's Avatar
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    Quote Originally Posted by Cass View Post
    What do you mean "1. We are installing a Bradford White heater for a customer." who is we...
    I'm a GC. Like it says in my profile My plumber will do the install.
    Last edited by dx; 12-19-2009 at 07:26 AM.

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    DIY Member SemiHandyRon's Avatar
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    I'm on the verge of having a BW installed professionally. Do the proper dielectric fittings "come with" the BW heater as a package deal, or do I have to trust the plumber to furnish the right ones himself?

  9. #9
    General Contractor dx's Avatar
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    I don't think I've ever seen a WH come with unions or any other "proper dielectric fittings". Bradford or any other brand.

    No, you don't "have to trust" your plumber, you can just tell him what you want done in specific detail and verify that he did what you asked Or, preferably, hire a good plumber and defer to his expertise.

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    Master Plumber Redwood's Avatar
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    Bradford White come with Dielectric Heat Trap Nipples installed.
    http://www.bradfordwhite.com/service...8_heattrap.asp

  11. #11
    Plumber Cass's Avatar
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    Today Most water heaters with 3/4" water ways come with dialetric nipples installed or with the heater...most with 1" water ways don't...

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    DIY Member SemiHandyRon's Avatar
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    Quote Originally Posted by dx View Post
    No, you don't "have to trust" your plumber, you can just tell him what you want done in specific detail and verify that he did what you asked Or, preferably, hire a good plumber and defer to his expertise.
    Far be it from a hack like me to tell a licensed plumber how to do his job! As I'm fond of saying, "I know just enough about plumbing to be dangerous."

    Thanks, guys.

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    Moderator & Master Plumber hj's Avatar
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    Default dielectric

    The nipples on the heater are "dielectric nipples", and they are no more effective than a dielectric union OR a Sharkbite, for that matter. A dielectric union or nipple DOES have a "break" between the different materials which a Sharkbite does not have. But a Shakbite does also not have the degree of separation which a longer nipple does.

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    General Contractor dx's Avatar
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    Quote Originally Posted by hj View Post
    A dielectric union or nipple DOES have a "break" between the different materials
    No the nipple DOES NOT. The nipple is steel. If I screw a copper fitting onto it, the steel and copper will be in direct and extensive contact (the threads) with no break. And they will both be in direct contact with the water.


    Quote Originally Posted by hj View Post
    ...which a Sharkbite does not have. But a Shakbite does also not have the degree of separation which a longer nipple does.
    Yes, but there is no direct contact between steel and copper. And what is the required "degree of separation"? Is there a mandated minimum length for a brass nipple? Code? Manufacturer's recommendations? How did you decide what is sufficient separation?

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    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by dx View Post
    No the nipple DOES NOT. The nipple is steel. If I screw a copper fitting onto it, the steel and copper will be in direct and extensive contact (the threads) with no break. And they will both be in direct contact with the water.




    Yes, but there is no direct contact between steel and copper. And what is the required "degree of separation"? Is there a mandated minimum length for a brass nipple? Code? Manufacturer's recommendations? How did you decide what is sufficient separation?
    Not touch is not touching....

    Pretty much every hotwater tank installed around here is installed with a brass or copper fitting right off the tank nipples. The tank won't last long enoough for the electrolysis to do enough damage to worry about it.

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