Originally Posted by vitauta
but i think i'm more likely to have a mineral deficiency than an excess.
Since the same water as comes out the cold tap is what goes into the water heater, and the water heater obviously precipitates out some calcium and magnesium, logically, you get more of the minerals from the cold tap. Not that they're any problem. The mineral content of public water varies a lot more than any possible difference between taps.
And you know the popular notion that one of the problems with ancient Rome was their lad plumbing. Seems it is unlikely to be the plumbing. For one thing, lacking faucets, the water ran pretty much continuously, giving it little time to pick up lead. (Thus the modern advice for lead pipe people to run the water for a while before using it.) And it's limestone country, which means heavily calcium carbonate lining the pipes. (We have the same kind of water, and old iron pipes are often found with only a tiny open channel.)
The Romans did indeed have a lead problem, but it was from the lead alloy linings of copper vessels (and wine was sweetened with grape juice concentrated by boiling in pure lead vessels) and the lead content of cosmetics, a problem that existed into the 20th century.