Tie up the ball valve that allows the attic tank to fill, then drain down the system by turning the hot taps on. Make sure the immersion heater and boiler are off though - although the copper cylinder wont empty completely you should do this. Then, break into the pipe you need to - expect some water spillage - and put an isolator valve onto the pipe. Then allow the system to fill again. With an isolator you can then work on the pipes at your leisure. An alternative to this is to actually freeze the pipe using a freezing spray - but you have to get a move on, and it depends if your nerves will stand it!
John, April 2008
