Originally Posted by ppro

I have microfiber cloths that I used to wipe the car immediately after washing. The product I use that removes the hard water marks is Meguiar's Ultimate Quick Wax, a spray.

Meguiar's Direct Ultimate Quik Wax


I spray it on the cloth, wipe the car to remove the water, then come back with another clean cloth, with spray on it, and dry the car. It puts a protective coat without damage to the clear-coat, and removes the water that contains the minerals that leave the hard water spots.