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thread sealant

PDB2 Member Posts: 26
In hydronic near boiler piping, is there a preferred type/brand to use

when mating copper to black iron? Or for that matter, a certain type for

all hydronic connections?


  • Snowmelt
    Snowmelt Member Posts: 1,334
    What I use

    Pro dope
  • jumper
    jumper Member Posts: 1,835
    technique can matter too

    especially with cheater thread
  • lza
    lza Member Posts: 40
    pipe dope


    Anything you use will be fine.  I personally use Hercules umm...Megaloc.  I like the consistency.  But pretty much anything will work (and my personal preference for application is a thin layer of dope, then a three wraps of teflon tape, then another thin layer of dope).  The one thing I would advise you on is your choice of fittings.  If you use dielectrics, stay away from dielectric unions as they tend to leak.  If you use a dielectric nipple, I personally always use a brass coupling and then a copper male adapter.  Copper female adapters tend to leak at the threaded joint. 
  • lza
    lza Member Posts: 40
    cheater thread?


    What is cheater thread?
  • hot_rod
    hot_rod Member Posts: 16,300
    I really like

    this 3- Wrap tape from Mill Rose. You really do not need to add any dope with it. Great for rough threads, and comes off the roll better, to the very end.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • bob_46
    bob_46 Member Posts: 813
    Cast Iron

    The use of teflon tape or paste is not recommended for connections on cast iron baseboard or cast iron headers on coils . It is too easy to over tighten and crack the casting .
  • RobG
    RobG Member Posts: 1,850
    edited August 2014

    If done correctly there is no problem with mating copper to CI baseboard with Teflon or paste, as long as there is room for linear expansion. At least I've never had a problem.

    And if you don't use Teflon or paste how are you going to seal the joint?