Chemworld Boiler Rust Inhibitor - 1/2 Gallon - Treats 125 to 250 Gallons of Water Boiler Rust Inhibitor - Treats 125 to 250 Gallons of Water Stops boiler rust. Compatible with Iron, stainless steel, copper, bronze, and PEX. P Indicator allows for product residual detection and leak detection. Compatible with most wood boilers.