Aside from magic, trolls, elves and other magical elements, Skyrim is basically medieval Earth.
I'm sorry but as a lore-freak I have to intercede here: Skyrim, Tamriel, Nirn, Mundus, and Aurbis are not basically medieval earth. Even if you try comparing timelines, it doesn't match up. For example, the history of human civilization is around 5,500 years going back to ancient Sumer. Civilization on Nirn goes back tens of thousands of years, and has all sorts of steampunk (dwemer) and magical (altmer) technology to make things even more complicated. Also, in those thousands of years people have learned to boil water to make it drinkable. Alchemists have been boiling and purifying water since the time of the aldmer / old ehlnofey, I'm sure the knowledge has eventually trickled down to commoners at some point in the past ten thousand years.