I store rain water in the basement for my house plants and Bonsai. In the winter I use that water for house plants, but in the summer it's a backup to the outdoor one under a down-spout. It gets stinky after awhile so I'd change it out periodically. But recently I got the idea to try putting an aquarium filter in it. It works like a champ, the water stays fresh all winter. It has an aerating capability too, if I set it at just the right height it will suck air from the surface and blow bubbles. I wouldn't feel bad about using that as drinking water in a pinch.