I was bored and had a look into the whole 'people in the Middle Ages didn't drink water' thing. Apparently that is indeed exaggerated.
While it is true that beer and wine were staple drinks, depending on which region you lived in, people commonly drank water all throughout history.
Most of it would've been well water i.e. ground water, which is relatively safe to drink since the soil serves as a natural filter. Wells are more likely to be contaminated from the surface than bottom up, so unless the soil itself was already contaminated to begin with, a well-placed and well-maintained well should provide drinkable water.[footnote]Fun fact, ground water is the largest source of drinkable water in the US and there are still many people who rely on wells for their drinking water in developing countries.[/footnote]
They may not have known about pathogens back then, but they did understand the importance of clean wells. Purposefully contaminating wells was a common scorched earth tactic in warfare since at least ancient times and some places apparently had local laws prohibiting outsiders from using wells. And at the very least, people knew not to drink dirty, bad-smelling water unless absolutely necessary for survival. There are also sources of historical medical authorities like Pliny and Paulus recommending boiling bad water or adding wine to make it safer, indicating at least educated people knew it helped even if they didn't know why.
However, people of all social classes did commonly drink beer, wine or mead. The beer they drank wasn't what we know today, but 'small beer', a beverage made in the same way as beer but with much lower alcohol content, and favored because it was a lot cheaper than a true beer. It was drank by men, women and children alike. In regions where grapes were grown, people, at least the more well-off ones, commonly drank wine instead. They often did water it down with up to 4 or 5 parts water to one part wine to offset the heavy alcohol consumption. Combined with the weak small beer, this indicates that, no, they didn't go around drunk all the time.
Some historical sources did recommend drinking beer or wine over water for better health, some indeed because it was deemed safer, but also because they were considered more nourishing. Which is true, since beer and wine contain at calories, while water doesn't, and of course they contain other nutritious stuff which water doesn't as well.
But, there were just as many sources listing water as a preferred drink, even over beer and wine. It was also a common practice at the time to punish monks with a diet of bread and water, which would've been pretty sadistic if they believed water caused disease, especially since monks would be some of the most educated people around and thus more likely to know. In any case, few, if any, sources advocated against drinking clean water.
Of course, the above mostly covers Medieval Europe. I didn't look into other parts of the world. People in Asia (and later the Middle East, then Europe) probably drank tea, but that in itself doesn't mean they didn't drink water.
Anyway, you guys will probably want a source. I checked a lot of them, but kinda forgot to keep most of them.
I still have the most important one tho.
It covers most of what I said. It's from Jim Chevallier, a historian specialized in food and comes with its own bibliography of sources. I have no reason to believe it isn't reputable.
I hope this helps.
