I am wanting to tie in to a galvanized water line with new copper pipe.the guy at the hardware store is telling me I need a dielectric union ? is there anything to this? at the start of the new line I will install a brass shut off valve,to me it seems like this will do the same thing as the union.
If I’m not mistaken, the dielectric union insulates the two dissimilar metals from each other. If they are not separated electrically, crud will build up fairly rapidly and clog the pipes.
That crud is corroding metal. The two dissimilar metals cause a reaction (like a battery) which corrodes the galvanized. He’s not blowing smoke.