Guys, there is a HUGE DIFFERENCE between the Storm Water Drain and the Sanitary Sewer systems.
You should not ever send wash water or anything but the rain down the Storm Water Drains, gutters, etc...
In the Sanitary Sewer systems in a lot of cities you can process your wash water and remove the oil/grease and dirt/sand/sludge and the "gray water" can be sent to the Sanitary Sewer system but you have to talk to your city's Wastewater department or whatever name the city you live in calls it.
There may be strict guidelines like filtering the wash water down to 5 microns or a lot less strict like 100 microns or larger but most want the oil/grease removed so it does not start clogging up the pipes along the way.
Check with your local Departments and see what their requirements are so you are compliant.