HARDNESS INCREASER Use 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 and heater. 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.