The 'smaller' water tank in the attic of my parent's house has started overflowing. I emptied the tank out and replaced the valve and all seemed well, but a few days later the same thing happened. I emptied the tank again and bent the arm of the ball-cock down and the valve stopped the water as it should but a few days later the tank was overflowing again. Each time, the ball-cock was submerged so I then replaced the plastic ball and guess what? - same thing a few days later.
I think this tank is to ensure the radiators are topped up so I don't really understand why the water starts to flow in the first place (no obvious leaks). I also can't understand why the ball cock gets submerged - when I'm there and empty the tank, the valve seems to operate fine.
I don't live close by the house so can't spend the time to see when the water starts to come in to the tank, I just know after a few days it starts to overflow.
Any Ideas? Thanks, Danny

Hi Danny

I am not real familiar with this type of setup, but if there is a ballcock in the tank then it is certainly reasonable to suggest that the ballcock washer may be bad and either the washer to the ballcock needs to be replaced or it may be that the entire ball cock assembly needs to be replaced.

Here, ballcock's can look like they are working fine, but a little tiny trickle is getting by the washer... can take a day to show up as in the case you present.

Go back to the tank and listen for a slight hiss near the water inlet to the tank. If you hear a hiss I think we are headed in the right direction with the info. Provided above.

Thoughts?

Mark

Thanks Mark, but I've already replaced the entire 'valve and ball-cock mechanism'. First of all I replaced the brass valve complete with the brass arm attached to the 'floating plastic ball'. Then I even replaced the ball in case it had somehow become porous or something as it's submerged each time the problem manifests itself. My next step is to replace the valve again just in case I've got a faulty one!
I apprecate your response though :-) Danny