Hi I am increasing the size of my heating system (loft convertion) and need to add another expansion vessel ( already 1 in the combi) I've managed to size the vessel requird but can't seem to get to the bottom of where to position it. I have been told that it needs to be as close to the boiler as possible but this is not easy for me space wise - it would be far easier to position it in the new upstairs. If it does need to be close to the boiler could someone explain why - i can't see the difference. Also should it be in the flow or return ( the 1 in the boiler is just straight off the tank) Any help would be gratefully received! Thanks