In Short

In general, you can drink water from watertabs everywhere. If the water is not good enough to drink there HAS to be a specific sign! You can drink it from:

• water tabs in restaurants, restrooms, public spaces
• waterfountains in public spaces/squares in the city: take the water as it comes out of the fountain, not the water that is sitting in the basin.

The rule is that water has drinking quality when it comes out of the tab. If you don’t see a sign you can drink it.

Relevant Link