Especially designed to prevent scale formation in spas and hot tubs. Features: Prevents scale formation Aids in the removal of existing scale Prevents dissolved solids from separating into spa and hot tub water Applications: Weekly: Add directly to spa. Use 2 oz. for spas up to 800 gallons. Use 4 oz. for spas over 800 gallons. Run filtration system for one hour, or normal filter cycle. Tips: Control of calcium can be very challenging, especially in spas. Regular use of Defender will prevent mineral buildup from occurring and causing the spa's heater or equipment to fail. Use as a follow-up to Metal Gon, applied at start-up. Compatible with: Chlorine, bromine, ozone and Advantage: Use as part of the Simple Spa Care Program