Since living in San Antonio, Texas since 1986, I have found only two products that work on our very hard water stains..Edfred Shower Stall & Tile Cleaner and Edfred Toilet Bowl Cleaner.
All the other products that I tried appear to work, until after the tile drys and there still is soap scum..with one application of the Tile cleaner my shower and bath tub are clean to the bone. There is no need for multiple applications. Edfred Toilet Bowl Cleaner- also cuts through the hard water "ring" with one dose.
I love this product so much I buy it and have it shipped to my house in San Antonio, because no one in the area carries it anymore....don't mess with the rest..try the best...Edfred....karen king