To remove hard water stains from glassware, wipe the glasses with a clean cloth soaked in distilled white vinegar, or soak the glassware in white vinegar for 15 minutes before rinsing. Use a rinse aid in the dishwater to prevent additional build-up once you remove the hard water stains.
Hard water stains typically appear as white stains or cloudiness due to mineral deposits from the hard water. Vinegar can removes those mineral deposits, and the vinegar smell disappears when the glassware dries. Some dishwasher manufactures have special detergent formulas designed to prevent or remove build-up of the minerals. These detergents and the special additives can help keep glassware clear without extra cleaning steps.