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Dielectric fittings in Hydronics copper to black

I am presented with my newest "promotion" to outside sales for a local Wholesaler.  This question was posed to me today.. again.  Before my wholesale career I was an installer for 20 years.  I never used dielectric unions in a closed loop system with the proper tubing installed.  Does anyone "Dan" have anything in writing!!!!

I have a large customer that has a new employee who was taught like me and is trying save the company lots of $$$ on a project.  All I have to do is show it to them in writing of an official document or training book!!

All help is appreciated! Reply Edit


  • IronmanIronman Member Posts: 3,406

    It may depend on the code that your jurisdiction has adopted. Our state uses the "international" code and it requires them. I'd recommend you contact your local inspector and ask for the code reference.

    Personally, I try to avoid them and use yellow brass instead which the code allows. I've never had a problem with brass, but I've seen and heard of many issues with dielectric unions.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • Dan HolohanDan Holohan Moderator Posts: 11,877
    I've never heard of a problem within a closed system.

    But then if the code says to install paper pipes, paper pipes are what should be installed. 
    Site Administrator

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    Hug your kids.
  • YvonneBYvonneB Member Posts: 14
    Thanks Dan

    Thanks Dan.. glad to hear from you!  We will have to catch up sometime.  I am header to the airport for a factory visit.

    Have a great day!

    Yvonne Burch
  • Dan HolohanDan Holohan Moderator Posts: 11,877
    Safe travels, my friend!

    Thanks for stopping by. 
    Site Administrator

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    Hug your kids.
  • jumperjumper Member Posts: 977
    why not?

    You have to connect some way so why not by the book? While on the subject why not add a little water treatment?
  • Steamfitter66Steamfitter66 Member Posts: 117

    they cause way more trouble than they prevent.

    1 stray current and bonding issues

    2 cheap rubber gaskets deteriorate quickly at elevated hydronic heating temps.

    3 additional joints to leak.

    Red brass would be best, Most yellow brass is of poor quality at least here.
  • YvonneBYvonneB Member Posts: 14
    Mechanical Code

    Hello All,

    Just to follow up, I have contacts in the Mechanical Code group, there is nothing pertaining to dielectric between dissimilar metals in the system.  Again, this is a practice that I personally followed for 20 years in San Francisco, Marin and Sonoma counties and never had an issue.  Yes, our company did and still does maintenance annually as called out in the Mechanical Code.

    Thanks again for all your input... until next time!

    Have a great Holiday Season!!!

    Yvonne Burch
  • Steamfitter66Steamfitter66 Member Posts: 117
    Engineering is generally the root

    Usually speced by a young PE wanna be. Or by a lack of understanding of electrolysis, and or grounding and bonding.
  • jumperjumper Member Posts: 977
    old engineer

    Well I'm an old engineer.The question is how long will HW heating system not leak when ferrous and cuprous are joined? Bronze & CI may be okay but copper soldered to steel?
  • YvonneBYvonneB Member Posts: 14
    No steel

    Steel should never be used in a closed loop system period.
  • Steamfitter66Steamfitter66 Member Posts: 117
    I spent 5 years

    Working at a large university where I was one of 6 in house pipefitters. We had many buildings with 5 to 100 year old piping systems that in places had copper to steel connections that gave much less problems than the several 5 to 10 year old buildings that had dielectrics.

    We had bod central steam and chilled water plants as well as some unitary equipment I have never seen electrolysis on steel to copper connection in a closed system. We had chilled, hot water, high and low pressure steam, high and low pressure condensate, etc.

    Open systems yes.
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