Every major city in southern california dumps raw sewage into rivers and oceans with regularity. There is too much of it to even keep track of. Here is massive one from not even 30 days ago: https://www.latimes.com/california/story/2021-07-12/la-me-po...

There is no municipal grey water systems or mandates. No reasonable person would say anything about southern california's water policy or water history is "responsibly managed". I don't know enough about northern california's situation first hand to offer comment but I would be shocked if it's any better. Oroville remind you of anything?

It is completely true that agriculture consumes many times more water than residential use. California is a complete disaster there too. 25% of irrigable water is diverted to the ocean for the delta smelt, and another 25-40% is controlled by the resnick family's holdings and the sham of the kern county water bank.

IRWD pioneered the purple pipe system and GWRS is the largest indirect potable reuse system in the world, but because the only means of unpermitted greywater use in California is from laundry machines, "No reasonable person would say anything about Southern California's water policy or water history is "responsibly managed"."?

What municipalities mandate greywater systems?

In the story you link the system discharged sewage into the ocean because it was overwhelmed with a unexpectedly large amount of debris that prevented 6% of the daily flow from being processed. In this case, it seems like the alternative was having the sewage overflow onto the land, which is a bit less desirable.

I believe if you don't divert water... you get salt water encroachment, which will poison fresh water aquifers.

Substantially less could be diverted to address that issue. There was much argument over the amount in the delta smelt litigation but probably as little as 1% would suffice for that purpose.

The Monterey Peninsula area has terrible water management. Sewage spills into the ocean have been a frequent problem. Despite the housing shortage, property owners can't get building permits due to a lack of water.

https://www.montereyherald.com/health/20180224/addressing-th...

There is no major city in California with ‘adequate supplies and management’ - they’re all irresponsible and failing. None have a decent gray water program, almost no new water storage has been built in 40 years, and they dump untreated sewage on a semi-regular basis (accidental of course).

I don't get the intense focus on grey water in these threads. Grandparent poster mixes up grey water and tertiary recycled water down thread, so maybe confusion over that or selective use of terms so Arizona comes out on top? Who knows?

Sure, Arizona seems to be leading in grey water, but treated effluent are exponentially higher flows and that absolutely is being used and applied in Southern California. GWRS is currently operating at 100 MGD of indirect potable reuse and in the midst of an expansion to 130 MGD and San Diego is currently building their indirect potable system to 83 MGD. All in addition to the 100s of MGD tertiary recycled water distributed via purple pipes and other means throughout the region. This is not to say the current status is sufficient(I'd love to see an exponential expansion on managed aquifer recharge), but seeing a number of recent threads opining as if no "responsible" water management is being done in the region, which is frankly, absurd.

I would be interested in seeing US cities rolling out and enforcing gray water systems.

Are they used at scale... anywhere in US?

Arizona. 2/3 or more of residential areas have and use grey water. It is a requirement for new construction in most if not all of the counties. Almost all of the water use you frequently see arizona criticized for, fountains, golf courses, etc, are all using grey water.