Diamond Crystal® Iron Fighter® Salt Block for Water SoftenersIn addition to hard water, many homeowners struggle with iron in their water supply. Iron can be found in city water supplies and in private wells. Rust stains, where there has been water, are a good indication that you have iron in your water supply. Made with typical 99. 6% pure salt. Virtually 100% water soluble, these water softener salt blocks are specially formulated to resist mushing and bridging in the brine tank helping to keep your softener