Dielectric or brass

JIMBO_2

Piping a new Smart-40 to a TT-110, the piping from the boiler to the tank is copper.  Would it be better to use a dielectric nipple/union at the tank connection or use a brass and connect to the copper? 

The same question for the domestic water connections atop the tank?  Any ideas?

Mark Eatherton

I vote for brass...

I've seen WY too many di-electric unions corrode themselves completely shut. What good is a union that can't be used as a union? And what good is a dielectric connection that actually feeds on itself?



Go yellow brass and be done with it forever.



ME

hot_rod

better be no or low

lead brass if you are in CA or VT. Else they lock you up



hr

MikeT_Swampeast_MO

Di-electric and Brass Unions

Hot Rod:



My experience is nothing compared to many here (including you), but I have worked on a number of vintage systems--including my own--that have been both heavily and poorly modified over the decades.  I've seen brass unions connecting copper with black iron; copper with galvanized and galvanized with black iron in use for 20, 30, 40 years or more and none of the unions or pipes they joined showed any unusual corrosion or scale.  I've also encountered such connections directly pipe-to-pipe without the intermediate brass union to find something excessively corroded, scaled, failed or failing. 



I have only installed two di-electric unions.  They were on a small electric water heater in an all-copper system and I used them because "someone said" that they were either required or necessary.  Guess what?  Within 15 years the di-electrics had corroded severely and one let loose in a severe way and over a long weekend (of course).



I only remember seeing two di-electric unions in a hydronic heating system--literally next door in a 1958 high-style "modern" home with its original Iron Fireman boiler.  When he was putting the place up for sale the owner told me the system had never required service but he had ignored a small leak near the boiler for years.  He had it fixed and when I went through the house nearly a year later to be nosy (it still hadn't sold and I was wondering, "Why?")  I saw dielectric copper unions on the supply and return and they were already corroding!  (The "why" didn't have anything to do with the boiler.  Despite very expensive materials and essentially perfect condition the house is just of very unusual design and difficult to furnish.)



Long-winded, fully explaining Swampy hasn't changed much...  I'm writing and researching for a novel and too much of my odd view on heat and energy were creeping in and causing distraction.

JIMBO_2

Thanks Swampy

Very interesting indeed.  I too wonder "why," but I figured to ask before going any further.  Considering the copper tubing between the stainless steel tank and the new boiler, I just do not want any trouble with either OR from Triangle Tube.