Citric Acid is a weak organic acid. A solution with a 6% concentration of citric acid will remove hard water stains from glass without scrubbing. In water treatment it is often used as a descaling agent for cleaning membranes, UV lamps and other equipment that is subject to calcium or hard water scale build-up.
Citric Acid Fine Grain is certified by NSF/ANSI Standard 60 for use in drinking water up to a maximum dosage of 125mg/L.