I know this is an old thread (not even sure how much is true!?!
) but my old house was fed by a cistern. I had a 10x10x10 or so concrete chamber in the ground. It was completely fed by my roof alone. It supplied ALL my water, bathing, flushing, cooking, drinking.
I'm in a subdivision now, but if/when I build out in the country again, I WILL be going back to the cistern way of life.