Gunk B232 Liquid Boiler Seal - 32 oz. GUNK is a local family owned company based out of Charlotte, NC. For more than 75 years, GUNK products, developed by the people who use them, has earned the trust of hard-working tradesment and the active DIYer through consistent, superior performance and a commitment to innovation. Will not deteriorate, lose it's efficiency, or discolor the water in the boiler system Forms a tough filling that expands and contracts with heat and resists pressure For use in either hot water or boiler systems