Scale Free Protects Against Scale & Metal Staining. Scalefree protects pools from the damaging effects of scale buildup and staining due to excessive calcium, iron, copper and other minerals. It works without the use of phosphates or harsh acids. Scalefree also works to prevent scale from forming on salt generator cells, helping to maintain optimum performance. Note: This product can be used with most sanitizing systems and is compatible with all pool surfaces. Do not use with biguanides.