Hercules Cryo-Tek 30 gal -100 Antifreeze is a ready to use 55% Virgin Propylene Glycol formula. It's designed for hydronic heating and cooling closed loop systems, most solar heating systems, snow melts, radiant heat and general plumbing systems. Plumbers have come to trust the Hercules offering to provide the highest quality of plumbing products. Contains virgin (not recycled) propylene glycol with triple protection corrosion inhibitor The triple protection inhibitor stabilizes pH to prevent corrosion, chelates, hard water minerals and inhibit scale and sediment formation Not for use with galvanized, CPVC or aluminum Used in systems fabricated with metal, plastics and rubber piping, fittings, seals and other parts For heating systems requiring freeze protection as well as corrosion prevention Cryo-Tek is GRAS (Generally Recognized As Safe) for incidental contact with food Will not burst to -100 degrees