This article is from the Europe FAQ, by Yves Bellefeuille email@example.com with help from Martin Rich M.G.Rich@city.ac.uk.
Tap water is safe to drink everywhere in Europe except Turkey. (However,
concerns have been expressed in the group about tap water in Russia,
especially St. Petersburg, and in the Canary Islands). In some cases,
the water may be "harder" (contain more minerals) than you're used to or
it may have an unusual taste, but it's still safe to drink.
Don't be misled if you see people carrying mineral water bottles: it's
quite common to fill these bottles with tap water, for convenience.