Why is overflow leaking again, had new stop cock and plumber already adjusted once..

[Summerwhereareyou]

Water running out shower dry, never happened before... Had new stop cock... All fine but then over flow leaking so he camel back hand adjusted a few weeks ago and now it's starting again..

Stop cocks are to turn water on/off, they don't prevent water running over the overflow level.

Check ball valve doesn't have a leak as this makes it heavier so sits lower.

Also, check it isn't rubbing against the side of the tank as that can stop it rising

And obviously, I'm assuming plumber has checked it cuts water off before reaching overflow outlet.

@billyt that's very helpful, thank you.