In medieval times, the common belief that people drank weak beer to avoid the perils of drinking water is a myth. In fact, clean water was available and widely drunk, with infrastructure like the Great Conduit and the New River supplying water to London. Public toilets and cesspits were used, and regulations were in place to prevent polluting drinking water. People drank small beer not for health reasons, but for energy and hydration due to its calorie content. Wine was a luxury for the rich. This historical perspective challenges common misconceptions about medieval drinking habits.
https://www.ianvisits.co.uk/articles/the-myth-of-medieval-small-beer-19763/