hi the pressure on your boiler should be about 1 .5 bar, the safety valve will lift at about 3 bar if this has gone over 3 bar then that is why the safety valve outlet is leaking, the safety valve should close when the pressure is reduced to a very low pressure.i would switch off the boiler and drop the pressure by turning the red safety valve head [knob] till the pressure is about between 0 and .5 barthen fill up the system to 1.3 bar and switch on the boiler.if its still leaking.fit a new safety valve about £15.00, to fit is very simple the baes of the valve has on its side a very small allen headed grub screw, undo this, after of coures turning of the boiler and releaseing the pressure,then it will pull out, it has an o ring to seal the joint,it takes a good pull to get it out but it wll come,it is not screwed it. ps twisting the safety valve head while under pressure can some times clear any dirt under the safety valve seat.DO NOT MESS WITH GAS. bob.
bob roberts, February 2006