On 18/01/2021 19:29, Peter James wrote:
I de-aired the Central Heating system today, a thing I need to do about once a
month. I did so from the towel rail in the bathroom, the highest point in the
system.

Following a suggestion from someone on this NG I lit the escaping air with a
match as the air was flowing out following the loosening of the drain screw.
It lit up like a gas welding torch and caused me to all but jump out of my
underpants.

Is there an expert on this NG who can tell me what this would indicate? And
any cure for the constant need to de-air the system.

The system is 20 years old from new, but with a new Worcester Bosch Greenstar
25i boiler that is one year old.
Peter


As others have said, it's hydrogen - which indicates corrosion.

But if you had a new boiler a year ago, didn't the installer do a system
flush and then add inhibitor? If that had been properly, you shouldn't
have this problem after only a year.

Is it a vented primary system, or is it pressurised? If the former, it
could be leaking and introducing fresh oxygen in the top-up water. Or it
could be pumping over and introducing air. If the latter, there could be
a problem with the pressure vessel. In this case, you would be aware of
having to re-pressurise it frequently.
--
Cheers,
Roger