SpaBoss Cal Rise is the effective way to increase the Calcium Hardness of your spa or hot tub’s water The best range of hardness should be between 150-275 ppm. Cal rise is granular and should be pre-dissolved in cold water before adding to the hot tub. Cal rise is pH neutral. High calcium hardness promotes scale formation and cloudy water, where as low calcium hardness promotes suds/foaming or water and corrosive water. Do not add Cal Rise if your water is cloudy or if your PH level is too high.