Down here at the beach, we have brutally hard water. The one product that I've found to remove waterspots was 3D's Eraser, that stuff really works. And, I haven't seen any problems with it. Hint: if it's really bad, keep rubbing with a MF towel and add product so that it doesn't dry on the paint. I had a 3/4 ton black Dodge truck that looked like fish scales get cleaned up this way!