In Store Only Increases hardness in spa water. Calcium is the ideal product to prevent and stop corrosion of equipment while increasing calcium hardness in your spa water. Directions for use: Hardness level should be tested often and maintained in the range of 100 to 200 ppm. If level is below 100 ppm, add 110mL of Calcium per 1,000L of spa water to raise hardness by 50 ppm. Pour Calcium directly into spa water while the spa is in operation. Wait 15 minutes before using spa.
