this sounds like an expansion problem,either the braided expansion hose or tee is blocked,or more likely the expansion vessel has lost its charge of air,all of which or a combination of all will cause water to discharge outside when the boiler runs. this is probably a job which is beyond a diy repair, but can be repaired pretty easily,and may also reuire the replacement of the 3bar blowoff valve if it will not reseat. as for the dhw dripping,this is another problem which needs attention,but would not cause the boiler to lose pressure, and you need to be sure this is where it is actually dripping from.
alan wilkinson
September 2007