Since being switched on after the summer my CH system has been making a right racket. Unfortunately I can\\\'t pinpoint where the noise is coming from. The combi boiler does not lose pressure any more than it used to, there is no noise when the CH is off and I am running hot water. The noise appears to be a dripping behind the wall and from the intensity it appears to me that the water is falling quite a distance. Is this a leak or is it the pipes creaking