working at a property today.servowarm 'heat only'boiler downstairs with pump next to it,all behind a swing-out radiator.looked in the loft at the top of this 3-storey terraced house and found the header tank minus one expansion pipe!followed the cold feed from the tank down into the bathroom and into a radiator!has anyone got a clue how this system has worked fine until the gas valve blew on the boiler?