On 19 Dec 2020 at 12:21:04 GMT, "John Rumm"
wrote:

On 19/12/2020 08:08, Peter James wrote:

Every three or four weeks I need to de-air the towel radiator in the
bathroom.
This is the highest
Radiator in the system.
A friend, who is a retired plumber, suggested that I have a small leak
somewhere in the system.

That's a possibility.

Another is that its not air, but hydrogen accumulating from corrosion
processes. Do you know if there is adequate corrosion inhibitor in there?
Yes there us, I watched the Engineer run it into the system
Peter