The satisfying loop have stopped working on my combi?
Answers: Your wadding hose should also have a non return tap, this can get stuck, I would suggest replacing it. But you requirement to turn of the cold water via the stopcock and switch bad the boiler and close all radiator valve (both sides need to be closed) afterwards close both isolation valves on the flow and return pipes on your boiler. Then drain the system down. Then its not detrimental to remove the faulty valve.
Note, you should also fix the leak (your system is leak water, hence your pressure keep dropping). check all connections / pipework and radiators for the dribble.
As you have topped up the pressure over time, you should also give new inhibitor too.(as your system my enjoy very little left).
Sounds close to the valve have got stuck on the wadding loop. Best call out a plumber to replace it. Sometimes a GENTLE thump with a sledge hammer will free it up but I mean GENTLE xxxxx
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