This product works on hard hard water!
Our sprinkler hit this window for a year. The water stains were impossible to remove. Tried CLR and other cleaning products, nothing worked.  After trying this powder, 15 minutes of scrubbing later I can see out the window again. So happy.  Great value. Easy to use. Has a slight odor.  The before and after picture says it all.  Thanks!
Rating: 5 stars