The cRc policy on buying Bottled Mineral Water on Pesach is:
All water is acceptable for Pesach if free of carbonation, flavors, vitamins or other sensitive ingredients (like caffeine and calcium citrate). However, the following ingredients are not an issue for Pesach: calcium chloride, magnesium chloride, magnesium oxide, magnesium sulfate, potassium bicarbonate, potassium chloride and sodium chloride. Please note that coconut water needs a special Pesach certification.