If it is because the flue terminal has rotted, Potterton make a Flue revival kit which comprises a new terminal and a sleeve for the inner pipe, you simply cut the sleeve to length and slide it over whats left of the old flue pipe, costs about £20, Wolseley Partscenter Nationwide will supply, (Will only sell to Gas Safe Registered Engineers - for obvious reasons)
www.elanar.co.uk, May 2009
