When DSM, Iowa flooded in 93 we lost our water plant for 2 weeks. What saved us is that it continued to rain and we caught water from the downspouts in plastic trash cans and used that water to flush the toilets and for cleaning up. I poured a little bleach in the trash cans every day. My husband actually figured out a camp-type shower for us.
See, I can't get past that bleach thing. They say to add bleach to the water and that just freaks me out.