"I think all buildings should have at least two water systems, ..."

And when the dog or the kids drink out of the toilet? *grin*... It has a nice sound to the idea, Ebbie, but the practicalities of plumbing and expense would be a problem.

Now for certain areas, where water is scarce and expensive, there are already various recycling setups. The biggest problem is expanding population and manufacturing and demand on systems like the Colorado river, where there is something like requests for 140% of available resources.