Expansion vessel in combi losing pressure. No water leaking from valve.

[Jake S]

The boiler is a Chaffeteaux Britony 80 Combi. The expansion vessel loses all pressure quickly.

After suspecting the vessel, I depressed the valve's plunger and found that no air came out. I pumped it up with a bicycle pump so that the pressure guage read 0.7bar more than it was before. An hour later, the pressure had dropped back to where it was, and no air came out of the valve when I depressed the plunger.

No water seeped from the valve when I depressed the plunger. I'm wondering if the valve could be the culprit. Are these the same valves that they use in car tyres? Is it as simple as going to a car spares shop and asking for a tyre valve?

Thank you,

Jake

[Roger Mills (aka Set Square)]

Did you do all this with the water system cold, and unpressurised? If not, you need to do that.

To test the valve, re-inflate it to 0.7 bar and then spit on your finger and wipe it over the end of the valve. A bubble will form if the valve is leaking. If the vessel loses pressure, but the valve *isn't* leaking, the vessel itself must be duff - in which case, I can't understand why no water comes out of the valve.