Seals and repairs cracks or leaks in steam or hot water heating boilers. Prevents steam boiler surging and will not clog or coat submerged hot water heating coils, controls, vents or valves. Makes a strong, lasting repair on difficult leaks in steam boilers. Tough seal expands and contracts with heat, resists pressure, and is not affected by boiler cleaners. Will not cause priming or foaming. Boiler liquid combines instantly with water in the boiler. As the water leaks through the crack, it is vaporized and the oxygen in the air transforms the boiler liquid into a strong, solid substance. The heat generated by the boiler further hardens the seal. Contains no petroleum distillates and is safe to use in boilers and systems with plastic or rubber components. Boiler liquid can be used on new installations to repair leaky joints, sand holes, etc., which may appear after an installation is completed. Ideal for older installations where corrosion causes leaks and cracks that need to be sealed.