Quick question, is there any other reason other than a leak somewhere on the central heating system, why i have to top up the pressure about once every other week? I keep it on one and a half bar, but after a fortnight its down to one bar. I live in a upstairs flat, and theres no sign of leaks on any of the downstairs ceilings. Thought perhaps there is a internal boiler leak into the hot water or summit but not sure. Any ideas?