Great topic. There are so many simple and potentially important ways people can become more self sufficient and at the same time prepare for emergencies.
About ten years ago, I purchased a Black Berkey water filter and have been using it to filter rain water that I collect ever since. And by that I mean that I've never changed the filters. By using only rainwater the filters seem to last indefinitely. But the thing is, I no longer have to rely on the city to provide water for me and my family. It may not rain as much elsewhere as it does here in FL, but people really only need a couple of gallons a day for drinking.
A few rain barrels and a good filter. An affordable and important step toward self sufficiency. .