Stain Drop No 2The Stain Drop No. 2 is a powerful stain remover specifically formulated to eliminate copper stains and scale buildup, common issues in pool maintenance. It effectively breaks down and removes these deposits from pool surfaces within 2 days to 2 weeks, depending on the severity. Ideal for use in chlorine based sanitizing systems, including saltwater pools, Note: Must be used in water temperatures 60F or higher.