overflow pipe dripping

[eowynk]

I am in the process of moving in to a new house and the overflow pipe from the cold water has been dripping. when you look at the tank the overflow pipe is slightly below the water line so i changed the ball cock thinking this was the problem. i then removed some excess water and watched for a bit. the in flow was not running so i assumed i had fixed it. no dripping for a few hours then after using some taps and maybe flushed the toilet i noticed it dripping again. when i looked again the water line had rissen again to the original level meaning some was going out the overflow pipe. but the inlet was not rinning or dripping. Help. do i need a plumber. suggestions please.

 

[seco services]

poss a mixer tap is passing cold mains to the hot and back filling the cws in the loft.
try isolating any cold mains fed mixer taps.

 

[denso13]

As seco says and could also be problems with coil in cylinder. Do you have a hot water cylinder? What type of heating do you have? Do you have another cistern in the loft apart from the one which is overflowing?

 

[bengasman]

Turn the stopcock/iso valve to the tank off before you go to bed, and see what happens.