I have a Gledhill pressurised system and it has started to vibrate when the cistern and pressure valve was changed after failing through the winter. I have had 3 different plumbers in and they don’t really know. It happens when the hot water is being used. The pressure is initially good and then sort pf settles but between those 2 events, that’s where the vibration occurs. All my taps are mostly mixers. I have watched it happen and the vibration occurs between the hot water pipe (taking hot water from the cylinder) to the white cistern which I believe is the overflow?! Both cistern and pressure valve (in red) have been checked and all fine. Yet, still vibrating! See photos.