MW wrote:
I moved to a house that is over a century old and noticed most of the
upper floor water lines to be
newer copper but the lower main lines galvanized steel

Won't this lead to rapid deterioration of the lower water lines?

I would also like to know general guidelines for avoiding galvanic
action on piping and so forth
I need to have a water heater installed andwas told to use fittings
which use a
mix of different metals in it's construction...
Why is this, and how does this negate galvanic action by merely being
a mixed metal fitting?

Thanks
Joe

As noted the problem is complex. Part of the formula is the water
(acidity salt content etc.) electrical grounding and others. The short
answer is if the plumber did the job right, it is not a problem. The problem
comes up when the plumber takes shortcuts or the home owner does not know
better. It seems you do.

--
Joseph Meehan

Dia duit