We have just had our boiler moved, having just had an extension built. Just recently, when the boiler has been on for a while, we started getting kettling noises coming from the boiler. If we turn the boiler off and back on again, everything is fine for 10 minutes or so, and then it starts all over again, and it does appear to be getting worse. It doesn't seem to matter if it's just the hot water or heating that is on. From what I've seen here, I would guess that the pump is not pumping the water sufficiently? Or possibly, the plumber has put the wrong kind of chemical into the system. The pump is running on its fastest setting... Please help - The plumber who moved the boiler is reluctant (a little understatement!) to get involved!