Canada

Relevant to this discussion I just moved from the LA area to Vancouver Island. Though there is a drought here no one from Los Angeles would recognize it as such.

The city in California where I lived had a water treatment plant whose output was used to irrigate city parks and landscaping. Not particularly practical to run a parallel water system outside a dense urban area. Maybe not even then. I was not aware of any individual homes that were using grey water systems unless it was some DIY kind of set up. The most I ever did was collect the water I used to wash rice or when waiting for the shower to warm up and use that to water my garden. Eliminating waste like that probably does little in the grand scheme but after living in a desert for so long I can not just pour water down the drain without trying to salvage some of it. Dual flush toilets can also cut down on waste or the tried and true "Don't flush for #1" . Even new toilets use 5L per flush so that adds up fast.