Features: Increases water hardness Helps prevent corrosion Applications: As Needed: One ounce raises the calcium hardness 7 ppm in 500 gallons of water. 1. Determine amount of product to be added. The ideal hardness level is 150-400 ppm. 2. Turn jets ON to circulate spa water. 3. Pour required amount into the water. 4. Run filter for 1 to 2 hours. 5. Retest water to ensure proper level. 6. Repeat steps 1-5 until proper level is obtained. Tips: Use Leisure Time Spa and Hot Tub Test Strips to determine hardness level. Water low in calcium will etch plaster and corrode equipment. Compatible With: Chlorine, bromine, ozone and biguanide sanitizers.