Leisure Time Defender is designed to prevent scale formation in spas and hot tubs. This product also aids in the removal of existing scale. Defender prevents dissolved solids from separating into spa and hot tub water. It is compatible with chlorine, bromine, ozone, and biguanide sanitizers. Regular use of this product will prevent mineral build-up from occurring, which could cause the spa's heater or other equipment to fail. Leisure Time recommends Defender to be used as part of the Simple Spa Care Program.