Triple protection Sentinel X500 Inhibited Antifreeze can safeguard hydronic heating systems in temperatures down to -40oF, inhibit the corrosion of all system metals, and prevent limescale deposits. Ideal for protecting hydronic heating systems located in colder climates, or unoccupied vacation homes, Sentinel X500 gives heating professionals and homeowners peace of mind that boilers and system components receive comprehensive protection year-round.


Sentinel X500 Inhibited Antifreeze’s market-leading composition has been endorsed by boiler and component manufacturers across the globe for more than 30 years. It’s unique blend of heavy duty corrosion inhibitors not only protect all system metals (including aluminium) against the threat of corrosion, but prevent the degradation of glycol, an occurrence that is typically caused by the presence of corrosion particles in circulating water. Further protection is provided by X500’s intelligent formulation, which contains multiple pH stabilizers to prevent large swings in pH that can otherwise cause and accelerate the corrosion of high value components such as heat exchangers and pumps.


Furthermore, with no less than three anti-scaling technologies, Sentinel X500 Inhibited Antifreeze ensures that hydronic heating systems located in hard water areas are protected from limescale deposits. Without proper water treatment, limescale can deposit on heat exchangers and pumps, lowering energy efficiency and causing excessive noise.


Sentinel X500 Inhibited Antifreeze boasts a non-toxic formulation that is based on propylene glycol, an additive that is classified “generally recognised as safe” (even for use in food) by The Food and Drug Administration (FDA). This is in sharp contrast to ethylene glycol, a compound found in many other antifreeze products that is a potent cause of acute toxicity in humans.


Consequently, Sentinel X500 Inhibited Antifreeze is a safe, robust formulation which provides very long-term protection. In fact, a properly designed, commissioned and maintained hydronic heating system containing Sentinel X500 (min. concentration 20% v/v) can provide 20 or more years of reliable service without the need to change fluid.


For the best results, systems should be cleaned and flushed with a suitable Sentinel cleaning product prior to the application of Sentinel X500 Inhibited Antifreeze. Sealed systems can be dosed via any convenient point if empty, or injected with a dosing bottle via the filling loop or other access point if partially drained. Open systems can be dosed via the expansion header tank or bypass feeder, or by using a dosing bottle if empty or partially drained.


Sentinel X500 Inhibited Antifreeze is available in 5 gallon and 10 gallon containers, and can be found at leading merchants throughout the country. For more information please visit