Blue Wave Calcium Hardness Increaser is used to raise the calcium hardness of pool water. Use hardness increaser as needed to raise the hardness (calcium) level in your pool to the ideal range. Prevents water from becoming corrosive and damaging your pool’s plumbing, heater and metal components. Stops staining and etching of pool surfaces caused by low hardness levels. Great for use in areas where soft water is a problem. Recommended dosage: 5 lbs. per 10,000 gallons to raise the hardness approximately 40 ppm.