I'm replumbing a home, and I have a quick question of when/where to use a dielectric fitting. The water main is coming through a bedroom, outside the interior wall. Starts galvanized from floor and goes to brass shut-off valve about midway. Trying to replace the easier galvanized with pex, but I want to avoid the UV exposure on pex, so completing the bedroom part of the run with copper until it gets to the attic.
So the entire run will be galvanized --> brass fitting (shut-off valve) --> copper --> pex. I know I need a dielectric fitting here, but would it be between the galvanized and brass, or brass and copper? Thanks