keeping the fresh water tank sanitary over the winter

I've often wondered about this, but I've never used my fresh water tank for drinking, or cooking for that matter. In another lifetime I used to fill my canteen out of a "water-buffalo" or a Lister bag, both of which had to be filthy, but water quality was way down on the list when the top priority was worrying about VC.

A few years ago I installed a water distiller in my home which is what I drink. I always carry a good supply with me on my RV trips for the same reason.