Susan ... thanks for posting the slow sand filter. Very practical. It won't remove everything, but could be very useful in a disaster situation. And it's pretty easy to construct. Maybe it would work even better if people mixed some charcoal with the sand - the charcoal might absorb some chemicals. Don't know if this would be an improvement. Just thinking out loud. Anyway, thanks for the link!

For water in urban sources, my own approach in L.A. will be to scavenge clean water from various locations such as water tanks, pipes, storage containers etc. I plan to work harder on developing this set of skills this year. I realized that I need a few items/tools
some garden hose
some sort of hand-powered pump
something that can drill a hole (or punch) through sheet metal

Pete #2