To remove hard water stains on glass, you can use commercial products formulated for these types of mineral stains, but there are also a variety of household products, such as salt, baking soda, vinegar, and lemon juice. Most cleaners for hard water spots on bathroom surfaces either dissolve stains chemically or mechanically through scrubbing. Chemical cleaners are usually acidic in nature, and mechanical cleaners are abrasive to scrub away stains. A combination of the two methods can also easily get rid of hard water stains.
Water is considered “hard” when it has a high concentration of dissolved minerals such as calcium, magnesium, gypsum, and other salts. When hard water dries on glass shower doors and other bathroom surfaces, it leaves white, chalky deposits of these minerals behind. Because hard water stains are caused by minerals that are basic in nature, many chemical cleaners contain acids to dissolve the deposits. Household acids such as vinegar or lemon juice can also be used; you can simply wipe the glass down with lemon juice or vinegar, allow it to sit, and then wipe it clean. Bleach is generally not needed for hard water stains because it is a base and will not dissolve the minerals.
Abrasive cleaners include brand-name cleaners, but you can also use baking soda or common table salt to scrub away hard water stains on glass. A combination of an abrasive and an acid can remove stains as well. Mix salt and vinegar and scrub the glass, then allow the vinegar to sit and dissolve the stains. You can also scrub the glass with a paste of baking soda and water, then rinse it with vinegar — the baking soda and vinegar will react and bubble away hard water spots.
To prevent hard water stains on glass shower doors or windows, you can treat the glass with commercial products or household items, but you can also use a water softener to remove the minerals that leave these chalky stains. Commercial products designed to treat car windshields can also prevent hard water stains by creating a slick surface that water won't stay on long enough to dry and leave hard water deposits behind. Household products that can perform the same job include baby oil and liquid car wax.