alt Hacker NewsHell if I know.
AFAIK the regulations were put into place to prevent untreated water from going into storm drains and into the water system, so presumably the cities are fine if you pour it down into the bathtub drain and let it go to the waste water treatment plants.
I appreciate the sentiment, but is the gunk on the car not the gunk that would have washed down the drains in the first place? Clearly there are plenty of nasty cleaning agents, but one supposes that safe ones might be used (I actually spent a while considering exactly this, and it's possible but not super easy getting an environmentally friendly car cleaner). I guess the issue is it's hard to tell from mere drive-by observation what cleaner is being used.