Rust Out® chemically removes iron and rust build-up that coats the resin bead and fouls the water softener. Rust Out changes rust and iron into a clear solution that easily rinses away and does not contain harsh or abrasive chemicals that damage fiberglass, porcelain or acrylic finishes. The advanced formula contains more than five chemicals that are formulated to clean, restore and maintain the life of water softeners. Rust Out can also be used to clean tough rust stains from toilets, sinks, tubs, white clothes and exterior surfaces.