If one could use tap water then why should one not use fresh water from the tap?
Answers
One of the most common causes of sickness for travelers on the road stems from being exposed to contaminated food and water. And one of the easiest ways for these bacteria and parasites to enter your body is through the local tap water. One thing you should definitely research before every trip is whether the tap water is safe to drink—it's something so simple, but so important for staying healthy.
While the majority of countries in Europe do have safe drinking water, there are few where you'll need to take precautions and some, where you'll want to avoid the water at all costs. In general, Western Europe has safe tap water and Eastern Europe is a place to be wary of the water. If you're unsure, take the time to ask a staff member at your hostel if the water is safe to drink or not.
When you're visiting any of the countries without safe drinking water, you should either rely on bottled water or you can take a look at how you can purify contaminated water on the road.