Tap water is safe to drink in Prague!
You can drink water from taps in Prague without worrying about the effect on your health. In parks and streets, you’ll see drinking fountains with clean water; don’t be scared to fill bottles with it. If the water from these sources weren’t safe to drink, such information would be clearly displayed.
Unlike in other European cities, in general, a carafe of water isn’t automatically served with a meal in Prague restaurants. You can order a glass, but don’t expect it to come cheap – a drink of water will cost more than a half litre of beer.