Hi all, My first post here, so my apologies if I'm asking stupid questions...basically I'm interested in buying a house, but the survey raised an issue that the boiler (a Worcester Greenstar 24i) had zero pressure. Now, the owner of the house is actually a retired plumber and installed the system himself - it used to have a cold water tank at the top of the house, but now has a large pressurized cylinder (in addition to the condensing boiler), approximately four feet high in the same room as the boiler. Firstly, I'm not exactly sure what this cylinder does but I'm assuming it holds hot water? Apparently it also has an immersion heater, but from what the guy said (over the phone) that doesn't appear to be its main function. Secondly, he said that water does tend to 'leak' out of the system (for lack of a better layperson word) and it has to be topped up. I'm fine with that, having had to do that myself on my boiler, but I wouldn't expect the boiler to be at zero pressure at any point? He's completed a full Landlord/Home Owner Gas Safety Record, with serial number, etc. but I'm still a bit confused by the setup of the system and why the Greenstar would be at zero. Does it sound ok to you professionals? Thanks, Sartois p.s. Some additional information from the completed record: the flue type is RS, the operating pressure was 18Mb, and the combustion analyser reading was 9.8.