Max, most boilers these days have a loop fitted, the tap to release water into the system will either be under the boiler casing connected between two pipes or else it may be hidden away in a cupboard beneath your boiler, turn the tap whilst watching the pressure gauge, each boiler make has a diffrent pressure requirment but most need to read between 1 & 1.5, though its best to check the handbook which came with your boiler, if you dont have a handbook try any search engine, just type in the make & model of your boiler.
John., December 2009
