Dripping overflow

[Kettletrout]

My overflow pipe starts dripping when we don't use any hot water for a while (eg overnight!). When we start using hot water again the dripping stops. Any ideas?

[jg96]

Check the ballcock valve on your header tank in your loft .As you use hot water that comes from your hot water cistern its topped up from the header tank and this is topped up via the ballcock. If it is not shutting off properly it will overflow.