Draining the system is always a good idea if the property isn't going to be occupied over a large period of time.
1. Identify isolation valve in attic and turn off (if none tie ball cock arm with string and a piece of wood so as no fresh water when replenish the tank)
2. Turn on all hot water taps in property, water needs to run from header tank, through cylinder then finally through taps. Then turn off taps.
3. As a precaution i would also isolate the rising main into the property(stop cock, normally located under the sink)
4 Turn off electrics to boiler and remove 3amp fuse, as the last thing you want is the primary flow and return pipes from the boiler trying to heat up air!!!...It'll go bang!!..
Job done.
Upon return open stop cock, remove wood/string from header tank. Allow header tank and cylinder time to get filled. THEN turn on taps (purge air through system) insert 3 amp fuse to boiler. Fire boiler up....BINGO..
1gas, January 2010
