On Wednesday, 17 July 2019 10:39:59 UTC+1, Steve Jones wrote:

The pressure in my volkera compact, about 7 years old, keeps dropping. I have replaced the expansion vessel whos diaphragm had gone, still drops. Not leaking from the pressure relief valve or the air release valve in the boiler and no signs of water in the boiler. I have tried isolating the boiler from the rads by shutting the isolating valves and it still drops, so assuming the valves are truly shut then leak must be in the boiler somewhere. Can it leak from the main heat exchanger into the condensate? If so how can I tell before I call in a gas engineer?

So you have a leak somewhere. Iso valves don't always iso. Anything can leak. Sounds like you need a good plumber rather than gas engineer. A pressure gauge on the other side of the iso valves would help narrow things down. You can also put fluorescein in the water & use uv to help see where it's leaking. I'm not a plumber, there may be better suggestions from others.


NT