Italian tap water is safe to drink everywhere. Italy has some of the strictest water quality standards in Europe. Rome alone has 2,500+ nasoni (the small iron drinking fountains with a continuously running spout) — free, clean, tested regularly, fed by the same aqueducts that supplied ancient Rome. Fill your water bottle. Stop buying plastic.
Tap water is potable (drinkable) in every Italian city and town. Exceptions: some islands (minor supply issues — check locally), some very rural areas (well water — look for "acqua non potabile" signs). Rome nasoni: 2,500+ free drinking fountains. The water is cold (comes from underground springs). Pro trick: Block the main spout with your thumb → water shoots from the small hole on top → drink like a proper Roman. Restaurants: You can legally ask for "acqua del rubinetto" (tap water). Some restaurants serve it freely; some push bottled water (€2-3 markup). It's your right to ask for tap. Mountain regions (Trentino, Valle d'Aosta, Dolomites): some of the cleanest water in Europe — Alpine springs feeding directly into the system.
Environmental note: Italy consumes more bottled water per capita than any country in Europe. You can help fix this by carrying a reusable bottle and using the 2,500 free fountains in Rome alone.