Hi - I have a pressurised domestic boiler system that seemed to be working fine before I had a house extension and several radiators added. The diverter valve failed once and was replaced and after this time, the pipes bang quite loudly when the thermostat switches in to stop the boiler. The banging only takes place when the radiators are on and seems to be in the area to the top of the boiler / divertor valve / pipes into the floorboards- there is no noise caused in Summer when I only have the hot water side working,a nd I have secured the pipes near to the divertor valve with brackets to the floor joists (to no avail).
The system seems to keep pressure well (it can be topped up from the rising main), but I periodically (perhaps once every month) have to bleed air from a few radiators (so air does seem to be getting in somehow).
Does anyone have any idea what could be causing this? I have had two plumbers in who were clearly lacking in ideas- one replaced the divertor valve, and another put a larger pressure overflow vessel in the system - both have made no difference!
Help Thanks Simon