dielectric nipple versus union???

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

  1. serge

    serge New Member

    Messages:
    12
    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. 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
  3. serge

    serge New Member

    Messages:
    12
    Location:
    Seattle
    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
  4. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    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 :)
  5. 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...
  6. 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.
  7. Cass

    Cass Plumber

    Messages:
    5,980
    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.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,251
    Location:
    Cave Creek, Arizona
    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.
  9. serge

    serge New Member

    Messages:
    12
    Location:
    Seattle
    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??
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,251
    Location:
    Cave Creek, Arizona
    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.
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