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.