Ferroli F24 Central Heating?

The pressure on our boiler is as high as it can go, which is about 4 and 1/2. There is a slow trickle of water going out the overflow pipe in the side alley.

I have tried bleeding all the radiators and releasing some water from them reduces the pressure but it only returns to 4 and 1/2 again.

This morning water was leaking from the boiler itself.

Any suggestions?

Clem Hardy, January 2011