Until someone else provides a more thorough answer, I’d recommend two prior posts. What is apparently a myth about the lack of availability of clean water and tendency to drink beer/wine instead is addressed here by u/Qweniden. u/idjet provides more links to other posts about the topic in his answer to this question.

If you search, you can find even more answers about all of a variety of aspects of water, although I haven’t seen any directly relating to how much relative to modern times was commonly consumed. What you will see in the answers above is that most of the population lived very near fresh water, and could refill it readily in the medieval era. Of course other systems, most famously the Roman aqueduct have existed for transportation.