Tap problem

[fergusq]

If I turn my tap off, it goes through the stopping point and then turns on full again - until I turn it again until it turns off. Ii is very difficult to find an 'off' point. When I take off the top of the tap, the valve bit that sticks up, is higher on the affected tap than on the good tap. But if I try to screw it down it works until that point where it 'pops' back out again. It sounds like some thread is broken, what could this be??? Thanks

[Harley]

It has gone past the internal thread inside the valve seat. You need to turn off the water,take the chrome shround off and then undo the tap at the brass top. You can then reseat the valve.

[Harley]

If my explanation is unclear there is a step by step guide here http://www.diydoctor.org.uk/projects/dripping_tap.htm