Sort:  

Thanks for mentioning me, mate😁

I would say that water quality of Czech mountain streams is very good as rivers rise there, so they are not spoiled yet. After all, it's no surprise that sometimes protected water facilities are located at foothills. When water arrives at cities, it naturally gets more spoiled, it's not definitely crystal clear as you could find in the mountains. Simply said, in the Czech mountains, I dare to refill my empty bottle with water. Anywhere else in the same country, I do not😉
Same principles could apply to Slovakia as well.

Thanks for shedding some light upon this topic :) That´s pretty much what I thought. However, occasional sračka is something that one should better be prepared for when drinking from rivers :D

sračka🤣 you nailed it🤣 Rivers as such, yes, except mountain streams and springs.