I have a problem with my central heating system - it pauses and then gurgles/adds water to the tank.
I'm on the ground floor, and there are only four radiators, I have done a lot of searching about information about this, and they all seem to say there is air in the system.
But I have bled every radiator and currently the main one in the lounge is switched off at both ends as the lockshield value is broken and needs replacing.
I have also drained and flushed each radiator getting rid of the sludge and added rust inhibitor.
Initially after re-filling and switching back on the system was fairly quiet and I did have to bleed one of the radiators multiple times.
Now it is back to being as noisy as before - all the radiators work and put out a lot of heat, but what I want to know is how to fix the gurgling? If it is air in the system - how did it get there and how can I remove it?