Glycol freeze protection fluids with built in inhibitors (designed for hydronic heating systems) should be used (do not use car antifreeze). These products are important in extreme climate applications and also in HeatLink® snow melt installations. A side benefit to these fluids is the lubrication/coating they provide to mixing valves and pumps. HeatLink propylene glycol is premixed with molybdate based corrosion inhibitor. A 20% glycol solution will provide the recommended molybdate concentration of 100-150 ppm. HeatLink recommends the use of 30% glycol for protected areas and the use of 50% glycol for snow melting systems. Higher molybdate concentrations are not harmful to the system. This product has low toxin levels. 5.3 US gal (20L)