Chemworld Outdoor Wood Boiler Chemical Treatment - 2x1 Gallon - Treats 700 to 1000 Gallons of Water Boiler Rust Inhibitor - Treats 500 to 1,000 gallons of fresh water P Indicator allows for product residual and leak detection. For use in most outdoor wood boiler systems. Compatible with Iron, SSTL, Copper, Bronze, and PEX.