I have a really annoying problem that has been bothering me for months I would be grateful if anyone could point me in the correct direction. In my bathroom I can hear water dripping and trickling continuously down pipes which have been boxed in down the bathroom walls. The bathroom has a dropped ceiling which houses a cold water tank. (No central heating boiler just a hot water tank with an immersion heater.) I have looked for the source of this noise for months with no success. No taps leaking, and as far as I can tell there is no leak elsewhere because there are no water patches puddles to be found and my downstairs neighbours have not complained of watering leaking into their flat. (I live on first floor of an Edinburgh Tenement block) Checked the cold water tank and it is not water running down the overflow, because the water level stops at a good few inches below the overflow pipe. The ball cock system seems to work with no continuous dripping of the valve. The noise can only be heard when in the bathroom and since everything seems to work ok with no-one complaining of leaks, I have just left it, but it is a bit of a mystery.