The water heater tank is a pretty good idea, but you need a way to seal it off in case of a boil water order. Maybe put in a bypass and only run water through the tank one day a week to reduce exposure.
Good point!
Actually in my case the water comes from a well, electric, into a 5000 gallon tank. From there, a pressure pump responds to demand and supplies the house. I added to this the (portable) 500 gallon tank and will soon add another. In addition, because my particular issue is power, I will add 2 more 5000 gallon tanks up the hill from me for gravity flow (I am rural).
Clearly a generator could power the wells but I may not want to draw attention to myself with the noise of a generator...
-carl