You definately have a leak somewhere. Firstly, check that the Pressure relief valve (PRV) is not letting water by.
If you cannot see it then it could be under the ground floor. You can put a leak sealer (fernox do one) into the central heating system, this can be squirted into a radiator and when you turn the system on, it should find any microscopic leaks and seal them - this may work.
Failing that, one easy way to find out whether the leak is on the boiler or on the pipework is to turn the valves off for the flow and return to the boiler (make sure you switch the boiler off first), leave it for a day - if the pressure doesn't drop then you know the leak is on the pipework, if it drops then it's leakig from the boiler.
Good luck.
Craig, October 2007
