Not ALL ideas Californians endorse are ridiculous. This makes sense.
I have been to Red-State communities that have been doing this for years. Their water is fine and actually is better than most communities that don’t use so-called “grey water.” The days of capturing mountain streams or pristine aquifers to pipe fresh to our taps are over.
Those days never existed. Most big cities are sited on rivers for a variety of reasons. Water supply is one of them. Most peoples' tap water is taken from dirty surface water.