If you have a pilot light on your combi, you will need to extinguish it. You should have a drain point on your system, on an outside wall, or perhaps on a radiator nearest an outside door. Opening this will drain down the system. To refill your system, if the combi has a pressure gauge on the control panel of the boiler, then you should have a filling loop somewhere on the pipework below the boiler. It consists of a silver coloured braided hose, with a quarter turn valve at one or both ends. Open these to refill the system, remembering to turn them both off when the correct system pressure is reached (about 1.5 bar).
Scott, December 2008
