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dielectric union on heat pipe?

i am connecting black pipe to copper on a oil furnace, steam heat system. should i use a dielectic union. do i need a special one for the heat. i can only find info on using them on water pipes but it always says to use them on dissimilar metals. thx

Re: dielectric union on heat pipe?

They are not need on heating systems. If that was the case all the valves on most radiators would not have been brass. Also most boilers are steel or cast iron and you would need dielectrics on all your connections to the boiler. On a domestic water system the are need as you stated.


Re: dielectric union on heat pipe?

thx john, i guess thats why i couldn't find anything about it. now that you explain it all i needed was a little common sense. TB

Re: dielectric union on heat pipe?

I had the same question.. Now I'm trying to understand why they're needed on water supply but not heating.. most obvious thought is that water supply is under greater pressure than heating system. With greater pressure, differences in expansion/contraction of metals are much more likely to cause leaks. However, won't corrosion still occur between the dissimilar metals? But maybe its slow enough that system should outlast the corrosion? Even TOH video on 'How to Convert Radiator to Multizone Heating' seems to use a copper to galvanized connection so mus be ok. How long will it last?

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