Overflow Pipe Leaking

[Jabbas]

Hi,

The overflow pipe connected to the cold water tank in my loft is leaking. It is definitely not an issue with the ballcock as I have checked it and it is not leaking. Also the water-level in the tank is not over the entrance to the overflow pipe in the tank... Could it be coming from somewhere else? It is not from toilet as the overflow pipe is separate. I'm at a loss so any ideas be much appreciated
Thanks

 

[bengasman]

... Also the water-level in the tank is not over the entrance to the overflow pipe in the tank...

I don't think it's possible for water to come out of an opening that is above the surface.

 

[cumbriahandyman]

Could it be from your central heating?