cold water tank not filling up - dripping all night - leak?

[MrsGorman]

We're having ongoing problems with our (plastic, 20 year old) cold water tank dripping from the inlet. The ball valve has been replaced and we've tried moving the ballcock to different positions. It never gets full enough to reach the overflow pipe. We turned it off overnight and it emptied which indicates there's a leak, but we have checked the pipes and the loo and can't find a leak anywhere.

Could it be a washing machine issue?

Any suggestions welcome!!

 

[Bahco]

Can't see it being the washer. Your tank will probably supply bathroom taps and cylinder.

Follow the pipes coming off the tank and see if there are leaks along the way.

 

[JayJay1978]

How many outlets has the tank got?

It must be quite a leak if it emptys overnight, min 25 gallons?

If it has more than one outlet (supplying cold taps aswell?) then if you turn off all the taps in the house and reach into the tank, when you cover the outlet with your finger you will feel the water going down the pipe.

This may narrow it down but we need more info.

 

[adlplumbing]

if you can`t find it then try agile he chargs 84 pound for diagnostic check and in your area

 

[ChrisR]

Could be "anywhere" of course, but it has to be somewhere you don't notice.
So I'd bet it's the loo overflowing slowly. If it's a modern one it'll be going down the back of the pan, so you may not see it.
To find that you'll probably have to remove a push-button on the cistern...
That'll unscrew, if you have one, or you may need to prize buttons out to find a screw.... guessing now!

 

[MrsGorman]

It actually is the loo. I double checked and the cistern is leaking consistently with the dripping from our loft!!