As I've posted before, I've already BTDT.
Back when I had the dealership, the powers that be gave me an earful about how I had to set things up to be sufficiently eco-friendly, and I had the same setup installed at my home when I built the home detailing shop.
And no, I never really gave it any thought before learning how things had to pass code at the dealership all those years ago...live and learn. There aren't any regs about it for residential situations in my area but it's just my version of doing things right.
I'm nobody's idea of a tree-hugger, but runoff going into storm drains/etc. simply isn't my idea of being responsible. But I *do* wonder just how bad biodegradable car shampoo/etc. really is
Left to my own devices, I'd probably worry more about the oil/grease/etc. that gets washed off of undercarriages and engines (and the sometimes nasty products that are used to do that sort of thing).
Water consumption isn't an issue in my area, which is supplied by a (presumably) inexhaustible aquifer.