Talking about saving water, my ex's family would reuse bath water.

They lived in the country and thus had well water. Often, in the summer, the water supply/well would run low or out so to avoid this they often would share bath water. She was the youngest so often be the last to use the water when she was growing up. She only had one older brother and her parents so not like a huge family, but I found it...well...gross.
I often remember going to the inlaws and when I'd use the bathroom the tub would be there full of water. There was a layer of soap scum and residue ring around the edge. The water was discolored, but it was well water, typically very hard and often cloudy, so hard to tell if very used.
Telling you this has made me realize that she has a good reason for being nuts.