dielectric nipple versus union???

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by serge, Jul 25, 2006.

  1. serge

    serge New Member

    Joined:
    Jul 25, 2006
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    lots of work
    Location:
    Seattle
    Hi all!

    I'm trying to update some of the plumbing in my house (1922). Most of the galvanized pipe has been removed, but there's still a few pipes. Some are in very good shape (i.e. no rust at all, clean water coming out) and some have to go! Ideally, I'd like to replace all of them, but can't rip out walls right now.

    Now to the question: if I update most of them with copper I know I have to use a dielectric fitting to join them, but do I have to use a dielectric union or can I use a dielectric nipple? I've heard about the unions leaking over time (we have some on our boiler pipes that do leak), but the dielectric nipples are just a solid piece.

    Any thoughts? Suggestions?

    Thanks,

    Serge
     
  2. Master Plumber Mark

    Master Plumber Mark Master Plumber

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    Feb 6, 2005
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    Sensitivity trainer...to be caring and loving to a
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    indianapolis indiana - land of the free, home of
    dialetric unions are a joke...

    I know this is going to raise an uproar,

    but I have never used a single dialectric union to

    tie into galvanized piepiing......


    always have used just simple copper female iron pipe
    adapters and never ever have I had any problems.....


    usually what I have found is the pipes seem to

    corrode shut at those unions. over time.............

    they corrode shut especially at the water heaters....at

    those dialectric unions..... I dont feel they extend the life

    of the heaters much either....


    just my experience and opinion only
     
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  4. serge

    serge New Member

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    nipples versus unions

    Boy, there sure is a lot of conflicting advise out there!!!!!:confused:

    It seems like most people recommend using some sort of dielectric juntion. There are these neat ones out there called "clearflow" that are rated for pretty high temps too. I'm tempted to use them in the connections from our boiler to the radiators and repipe the whole system with copper!

    Serge
     
  5. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

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    Columbus, OH
    Actually installed a HWH about 10 years ago and lost one of those unions. Just threw in a copper threaded adapter to get by...still working just fine :)
     
  6. Master Plumber Mark

    Master Plumber Mark Master Plumber

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    simple copper fittings work for years and years

    what you have seen seems to be my experience too

    run into tons of male adapters going into water heaters

    that are in reall good shape, but the dialectric unions are always

    a rusted up mess, we go onu on many service calls jsut to

    rheem out those unions to get flow through the heaters...
     
  7. Dunbar Plumbing

    Dunbar Plumbing Master Plumber

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    Service Plumber, Outdoor Temperature Relief Owner
    Location:
    Northern Kentucky/Greater Cincinnati Area
    I started out using MIP's into the ports of tanks years ago but code requires dielectric unions for the past 10 years on all water heaters installed in KY.

    I agree with their use but I'm disappointed that they are made of galvanized. You'd think someone out there would come up with an all brass dielectric but then someone would be out of a job I'm sure.

    I use the female dielectrics. Most water heaters come from the factory with dielectric nipples (which are galvanized) with the plastic inner sleeve.

    When I use a female dielectric, I try to tighten them down as much as possible, thus leaving a significantly smaller exposed area of galvanized to be exposed to the water. They still clog and the only remedy I've seen to avoid this is to cut a replacement dip tube off at 2" and it acts as a sleeve to prevent buildup on that 3/8" of an inch left of the DUF.

    Dielectric males can clog in 5 months depending on water quality. I sold a ton of them off on e-bay. They would be okay if they had plastic innards like the dielectric nipples.

    Whether I get my water heaters (not many these days) inspected or not I am forced by the codes in my area to use them. I don't want any reason for anything to come back at me down the road if another plumber does work for the customer and notices any shortcuts I made.

    I agree that the copper MIP's work just fine.......they want that separation of metals I believe for possible issues stemming from electrical paths taking off of the ground of electrical systems.

    Most times where I've seen massive corrosion at the top of tanks, no dielectric unions were present.
     
  8. Cass

    Cass Plumber

    Joined:
    Nov 12, 2005
    Location:
    Ohio
    I stopped using the galv. unions quite a while ago. All I use now are the insulated nipples with a copper female adaptor. I can't tell you how many unions I have had to ream out so someone could get good flow from the water heater.

    A brass nipple would work but the insulated nipples are cheap and have worked fine for me and I don't have to worry about any dialetric action at the tank connection.

    As a note of interest, I have noticed on other peoples work where they have joined copper to galv. that when they used teflon tape and used enough of it it seemed to be adaquate to prevent any dialetric action, I am guessing, by preventing any direct contact with the 2 metals.
     
  9. hj

    hj Moderator & Master Plumber Staff Member

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    dielectric

    Dielectric unions and nipples are strictly cosmetic. They do very little to break the electrolytic action because they are too short to really disrupt the flow of electrons through the water between the two materials. A 6" or longer brass nipple is much more effective.
     
  10. serge

    serge New Member

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    6" nipples

    I've heard that some code allows for a 6" brass nipple, but I can't seem to find much information on that and anything about whether that really corrects for the dielectric action??
     
  11. hj

    hj Moderator & Master Plumber Staff Member

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    brass

    Brass is intermediate on the Nobility scale between copper and steel. If it were not a good transition, every valve would have to be installed with dielectric devices on either side of it regardless of whether the pipes were copper or steel.
     
  12. Ron Anderson

    Ron Anderson New Member

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    Location:
    California
    Dielectric unions work very well at stopping current flow caused by dissimilar metals in plumbing systems. This small current loop is very similar to a battery circuit in a flashlight. If the switch is held open (off) then the battery lasts much longer. I didn't say it lasts indefinitly, it will eventually fail even if never used, because of the acid electrolyte will eventually consume the two disimilar metals. This is exactually what happens in piping, the electrolyte (the water) is generally acidic and will provide a small looping electrical path through the two joined disimilar metals and back again. This current although small will eventually consume the lesser noble metal (steel) and eventually clog completly or leak. The dielectric union provides an electrical break thus protecting the pipes longer. You notice I said longer not indefinitly, thats because the acid in the water will eventually consume the metals regardless of this fitting. When you buy a new car you never think of the starter battery as being permanent for the life of the car, because its a consumable just like tires. Dielectric unions are kind of like that, namely consumable, but its far better for the corrosion to occur in piping rather than at the water heater interface. By the way while on the subject, dielectric NIPPLES are just about worthless because the do not break the circuit at all. The only thing that they do offer is a slightly longer circuit path through the water. Also if you think you are doing yourself any good by using brass or bronze nipples, guess again they are both copper alloys and are practically the same as if you had used a copper nipple.
     
  13. Reach4

    Reach4 Well-Known Member

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    Sep 25, 2013
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    IL
    I have wondered about that myself. Since you mentioned the path through the water, that would seem to explain why the dialectic nipple, with insulation on the ID only, would actually work. But the report of rusted mess is based on experience, and that seems to trump "it seems". On the other hand Master Plumber Mark sometimes removes water heater anode rods, so maybe that affects things. I am a believer in anode rods for water heaters, and I replaced my eaten-up anode with a powered anode.
     
    Last edited: Feb 3, 2015
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