I have an overflow pipe on the outside wall which water is trickling out from.this pipe is connected to a wall from the cold water tank in an airing cupboard in the upstairs bathroom. The ballcock iis still connected to the tank it doesn't look as if the tank is overflown as the water is not spilling out and is at the normal level. What do I do? And where is this water coming from? Help me!

What part of the world are you in?

Hey Doug! Bet he's from "jolly old England".
Sounds like the ballcock needs adjusting to a lower level in the tank. If the overflow has any water in it then the tank's too full. If you can't adjust the ballcock then shut the water off to the ballcock and replace it. Good luck, Tom

Hey Tom, UK ballcocks are pretty much like ours, you can just bend the brass rod if there is not adjustment. I am going to catch it from someone for advising to bend your rod on your ballcock.