My proposal is very simple, every year thousands of gallons ofrainwater. are lost in the roof drains. in some places is used for irrigation in gardens etc, most goes to the drain.
but this water is very clean, in the country, we can drink it without problem, but in the cities,
the idea is to store rain water (or snow) in tanks above the buildings, keep it with chlorine tablets, and with a simple charcoal filter, added to each home network, add the water to our network (with less consumer spending) and we can use it to drink.