What Is Inhibitor...



Inhibitor is a chemical that is added to your central heating water. It has a number of jobs that are crucial to the reliability, efficiency and lifespan of your heating system. 

When your boiler was installed the installer should have calculated the amount of inhibitor required and added it to the system. On the annual service the engineer should be checking the concentration of inhibitor to ensure it is fully protecting the boiler and heating system. 


The inhibitor does the following:


  • It prevents the water in the system from rusting the radiators and other steel components which produces the black sludge you can see in the radiators. 


 I've recently replaced an oil boiler for a customer that was only 3 years old, the installer didn't add inhibitor and the service engineer didn't check for inhibitor. The boiler was replaced because it had rusted a hole in the top of the boiler, this oil boiler should have lasted at least 15 years before there was any concern about leaks. 


  • It prevents biological growth in the heating water, again this sludge blocks the small waterways in the boiler and pump. 


  • It provides a slight lubricating property that extends the life of the pump, valves and rubber seals in the heating system.