There can be many reasons to drain a central heating system, for example you could have a pipe or a valve leak that requires repair. It could be the installation of a new boiler. The process is not too difficult. However if you need to do this and are not confident, you should call a professional like a Catford Plumber who use trained people, and can carry out the job. So before you begin you will need to: Isolate the boiler so that the pump will not run. Wait until the water starts to cool. Isolate the main stopcock to the supply feeding the expansion tank. For extra safety, in the loft you should tie up the float valve in the feed and expansion tank using a wooden batte and string, this will stop the system from filling. At a radiator closest to the front door, connect a hose on the drain valve and run the other end through the front door and out to a drain. Tie the hose securely so that it can’t fall of the drain cock. Using a supply of old cloths around the drain cock, use a spanner or a key to open up the valve. Catford Plumbers always carry the correct tools for any occurence. Watch both ends of the hosepipe, especially the end of the drain cock. Once the water stopped running from the end of the hose, go from one radiator to another slightly opening the bleed valves, so that the last dregs of water run out. When you have made your repairs close the drain cock and the radiator bleed valves, remove the stick and string from the tank, and turn on the main stopcock. Working from the topmost radiator, bleed each radiator in turn. Finally you must bleed the pump and of course tidy up any mess that you have made.
