Yes it shouldn't end up in the waterways. I use blumats so no runoff to deal with. The plants that I do hand water I dump the runoff around the yard which isn't much. I don't use bloom boosters so I don't have high P runoff. I don't put the runoff in my vegetable garden which is 100% self sustaining organic. I pour it around landscape plants, roses, etc...
You bring up a very important issue about what people are dumping down their drains. I think most don't have any idea how damaging some of the stuff entering our waterways is to the ecosystem. That's why most detergent manufacturers have stopped using it after 17 states banned phosphate containing detergents and it's also banned in several countries. The thing with phosphates is they do a good job at cleaning. I recently got some TSP which used to be trisodium phosphate. Now it says phosphate free in big letters on the package. Oregon was one of the 17 states. It doesn't clean as good as the old stuff either but I don't mind putting a little more elbow grease into the scrubbing to help protect our waterways.