I have an existing gravity fed from wood stove hot water system, but no C/H. I have now installed 7 radiators and want to hook these up to a new GAS boiler. I would like to combine the H/W supplies so that when the fire is lit it will switch the supply over to the wood stove. Possibly through a thermostat on the H/W tank. Also as the Gas boiler needs a mains pressure water supply I plan to move the existing expansion tank for the wood stove from the loft to the downstairs airing cupboard (site of H/W tank and GAS boiler and use one of the existing feed pipes to supply the GAS boiler with necessary mains pressure water supply. This would save extra plumbing work and possible floor or ceiling removal to gain access. I don't see any problems but would appreciate any advice or comments. Eddy