Can I have a bit of advice as to how to resolve this - Every morning the main cold water storage tank overflows a small (I mean not a raging torrent) of water until we start to consume some of the water and the level in the tank drops. What seems to be happening is that when the ball cock is lifted up to it's maximum with the rising water level, the valve does not shut off completely and this then allows the water to ever so gradually continue rising until it reaches the overflow and this is where the problem seems to be. Question is, is will I have to change both the ball cock for a more adjustable one and also replace the shut off valve or do you think that a more adjustable ball cock alone will do the trick?. If I pull the ball cock up with my hand the valve shuts the inflowing water off (albeit I have to pull up with some force for it to do this), but relying on the ball cock and rising water level alone will not shut it off.