Originally Posted by OKC-XFR
There were concerns years ago that some automatic car washes would recycle their waste water after a cursory filtering - basically forcing salt water into areas that it would never normally get into...I don't know if that practice is still going on.
I believe that car washes recycle the water and the salt dissolved in it. I get outside with the hose when I can if it gets above freezing and hose the car down. Underneath is where the salt gets mixed in with all the silt and sand that lodges behind the bumpers, on top of muffler and in the fenders and suspension. Wash the bottom pan as well if you can stand the cold spray in your face. I have seen too many cars get lighter as the rust eats them away.