Tap water is fine.
ru-bi-NET-to — four syllables, double 't', stress on third.
In a casual pizzeria setting when you do not want to pay for bottled water and are happy with tap water.
'Acqua del rubinetto' = tap water. In Italy, tap water is safe to drink in virtually every city. However, many restaurants prefer to sell bottled water. In a pizzeria, especially a casual one, asking for tap water is perfectly acceptable.
Una bottiglia d'acqua naturale.
A bottle of still water.
Standard alternative — 'naturale' = still, the most common restaurant water choice
Acqua liscia, per favore.
Still water, please.
'Liscia' (smooth) is a regional synonym for 'naturale' — common in central Italy
Mezzo litro di acqua frizzante.
Half a litre of sparkling water.
Standard carafe size in casual restaurants
Italian tap water ('acqua del rubinetto') is among the most regulated in Europe and is safe to drink in all major cities. Naples has historically had water quality concerns, but modern infrastructure has made even Neapolitan tap water safe. Still, many locals prefer bottled water there.