We have an electric boiler which is in the airing cupboard next to the bathroom. Recently (in the colder weather) there has become an increasing loud banging/tapping noice coming from behind the bathroom wall. This sound happens at random (i.e. doesn't seem to be linked to the boiler heating up, toilets being flushed or taps being used). It didn't occur in summer at all and seems to be getting steadily worse. Assuming it is the pipes leading from the boiler to the bathroom, we can't access them unless we break down the wall (one side of which is fully tiled). I have read some of the responses re: banging noises on this site but they seem to all relate to gas radiators. Does anyone have any idea what might be causing this and how we can fix it (preferably without tearing down the wall!)