[inglor_cz]

"access to clean, probably distilled, water supply"

A good antibacterial filter + boiling that filtered water just to be sure goes a long way. That equipment is nontrivial, but for someone in a developed economy, usually affordable. Probably cheaper than being sick often, because even European welfare states often won't give you anything for first days of sickness.

[taeric]

The good filter is again largely to my point. :D

You are correct that boiling it can probably help a lot. You then have to store it in a clean spot for it to cool to a temperature you can use, of course. Something that probably relies more on modern technology than makes sense.