It is a common misconception that in the Middle Ages they drank ale because the water was dirty.
First of all, you would die. You would become dehydrated. You need water. Alcohol will leave you dehydrated.
Second of all, Europe still has clean water to this day.
There are ten times as many people in Europe today than there were in the Middle Ages.
There are cars and factories and mines polluting the water today.
And yet Europe still had clean water.
In the Middle Ages the water was a hundred times less polluted.
If they can find clean water today, how much easier was it to find clean water in the Middle Ages!
Where this misconception comes from is that in the ancient Greek world, people flavored their water with low-alcohol-content wine. The alcohol content was low enough that you could use it as a source of water and not get dehydrated.
This was because in the ancient Mediterranean, and in the Mediterranean to this day, grapes and wine were and are an important source of calories. The grape vine grows in poor soil that will not grow grain. So does the olive tree. Mediterranean civilization was based on this. And two thousand years ago, before we got really good at making wine, the wine did not taste good straight. So they watered it down.
This practice spread to medieval Europe. It probably did help keep people from getting sick from things in the water. But it did not mean that they had dirty water.
It meant that when they did use this practice, their water was even safer than ours. But they had plenty of good sources of good clean water.
Have fun with the new information!
Sincerely,
David S. Annderson