Boiler Rust Inhibitor is a highly concentrated liquid buffered Nitrite/ Borate/ Silicate inhibitor designed for closed loop or open loop Woodstoves or Wood Boilers with minimal water loss. It is: Designed to work in most makes and models of outdoor wood furnaces, woodstoves, and commercial and residential boilers. Formulated to provides proper corrosion protection for copper, mild steel, stainless steel and aluminum. It may be used with either hard or soft water and is compatible with glycol anti-freeze. One gallon will treat 500 to 750 gallons of make-up water. Contains a P Indicator for ease of proper dosage detection (turns your water a light pink). For systems closer to 500 gallons or if your ground water is low in alkalinity the water may not turn pink, although there will be adequate corrosion protection. Safe for yearly storage if stored in cool, dark area. $1,000,000 product quality insurance quality! ISO manufactured! Just add direct to your system. Product meets all D.O.T. shipping regulations.