How Did Roman Soldiers Survive Weeks Without Clean Water?

How Did Roman Soldiers Survive Weeks Without Clean Water? The march has been going for six days and your mouth tastes like iron and dirt. Not because you've been injured. Because the water in the ditch three miles back tasted like iron and dirt, and you drank it anyway, because the alternative was not drinking. You are a legionary of the third cohort, somewhere in the middle of a column that stretches so far ahead and behind you that the front and rear are theoretical concepts. Your pack weighs somewhere north of forty Roman pounds. Your sandals have put blisters on top of blisters. And in the leather flask hanging against your hip there is maybe half a pint of something that is technically posca and technically the entire Roman army's answer to the question of what do you drink when there is nothing safe to drink. You don't know it's working. But it is. Barely. Hold on to that flask. We'll come back to it.