Dielectric unions and water heaters

Discussion in 'Water Heater Forum, Tanks' started by dx, Dec 18, 2009.

  1. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    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.
  2. steelers fan

    steelers fan In the Trades

    Messages:
    49
    Location:
    va
    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
  3. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    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: Dec 19, 2009
  4. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

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    1,143
    Location:
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    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
  5. hj

    hj Moderator & Master Plumber Staff Member

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    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.
  6. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    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: Dec 19, 2009
  7. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    I'm a GC. Like it says in my profile :) My plumber will do the install.
    Last edited: Dec 19, 2009
  8. SemiHandyRon

    SemiHandyRon New Member

    Messages:
    46
    Location:
    Fairfield, OH
    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. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    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.
  10. Redwood

    Redwood Master Plumber

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  11. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    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...
  12. SemiHandyRon

    SemiHandyRon New Member

    Messages:
    46
    Location:
    Fairfield, OH
    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." :p

    Thanks, guys.
  13. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
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    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.
  14. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    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?
  15. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    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.
  16. johnjh2o1

    johnjh2o1 Plumbing Contractor for 49 years

    Messages:
    1,143
    Location:
    South*East
    We are seeing the nipples supplied by the heater manufacturers fail before the heater. Take a look at these nipples they are not sch 40 steel nipples.

    John
  17. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
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    Here the water conditions are good enough that the dielectric nipples are sufficient.

    However in some areas the water conditions are poor enough that the dielectric nipples are not enough.
  18. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,831
    Location:
    Cave Creek, Arizona
    nipples

    Dielectric nipples have a plastic liner that is supposed to provide the break between the parts of the tank and the pipe in contact WITH the water. WATER is the electrolyte which powers electrolysis, not the mere fact that two materials are contacting each other. You could screw a steel pipe into a copper fitting and set it on your workbench, then come back 100 years later and they would be the exaCTLY same, except dirtier.
  19. SemiHandyRon

    SemiHandyRon New Member

    Messages:
    46
    Location:
    Fairfield, OH
    What would be in the water for it to be considered "poor" in the sense used here?
  20. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    Better look again. The Bradford heater I just bought has steel nipples. No liner on the nipples, just the heat trap retainers.I don't know if the nipples are separated from the rest of the tank and it doesn't matter.

    The nipples are steel and they sit in water. If I connect copper fittings to them, there WILL be galvanic cells and the nipples WILL corrode.

    Edit: Still curious, how did you decide how long of a brass nipple is "sufficient separation"?
    Last edited: Dec 23, 2009
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