Hi all , the system is a conventional boiler with gravity dhw and pumped heating , there is a small primatic cylinder and the cylinder is leaking , The cylinder has to be replaced which is where the problems start the house is a dormer bungalow and the cylinder is in a void upstairs , the smallest primatic cylinder available is to big and wont fit in, so I thought about putting a normal cylinder in and adding a header tank but cant get any pipes from the loft down to the cylinder, so now I am thinking of a normal cylinder and making the heating circuit a pressurised system by adding a filling loop and an expansion vesel ,question is will the gravity water work ok or will it have to be fully pumped and will the antiquated boiler take the pressure ok ???? .