Nero Kalo (water good)
Nero Kako (water bad)
To Nero Peen-Eteh? (The water is potable?)
This is pretty simple folks: Do what the residents do and ask first! The water is safe to drink in most localities particularly Athens and the larger cities. On some islands with very little water like Aegina or Syros, the water is not safe to drink but it is safe enough to brush your teeth, shower and wash your dishes and hands with. Its always best to make sure by asking the local residents. On Syros, where a friend of mine is head of the water filtration plant, the water is partially desalinized so it wont make you sick unless you drink a lot of it but will taste salty. Some areas of Greece are very arid and there is no water particularly on some of the smaller islands. Some larger islands on the other hand, have plenty of water, so its up to you to check and make sure. Its no where near like Mexico however where I became annoyingly ill from the shrimp cocktail sauce.
Bottled water is very common in Greece but is an unregulated industry and not checked by the government. There are many domestic Greek and imported bottled varieties to choose from including fizzy and imported waters from France, Italy and other places. I have never gotten sick from the water in Greece and no one I know has either.
On the mainland, Greece is invariably mountainous, and that means plenty of local spring water, often there for the taking as pictured above. In restaurants do not order imported bottled water if you are in a mountain village - go with the local water! To Nero Peen-Eteh? The water is potable?