Earlier quoted context omitted.
You're just shoehorning in the assumption that people had diarrhea a lot, because that's the trope about medieval Europe. But if everybody lives in a well-established traditional way (and there's no current war or plague in the area) then they will also know by tradition the springs, streams and wells that yield clean water. In Georgian times, around 1800, coal-based industry gets under way, there's a population expl…
Even "natural springs" could give you tons of diarrhea due to some animals taking a dump nearby.
And I have also thought of the same point on my own before.
And it's not just:
>could give you tons of diarrhea due to some animals taking a dump nearby.
But also: from all the way upstream (from aquatic animal life), and from the upstream watersheds (from terrestrial animal life), which, all together, is a shit-ton of dumps, pun not intended.