Whilst rad valves will sometimes stop leaking with water in the system in your case there is, we now learn, air!
In that case I will modify my reply that I expect that the air has dissolved over a short time onto some residual water in the pipework.
Its not usually recommended to test with air to much pressure at all in case something bursts. In any case the small molecules of gas are much better at finding minute leaks.
Tony
In that case I will modify my reply that I expect that the air has dissolved over a short time onto some residual water in the pipework.
Its not usually recommended to test with air to much pressure at all in case something bursts. In any case the small molecules of gas are much better at finding minute leaks.
Tony