Boiler expansion vessel

25 Jan 2019
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United Kingdom
I have a question about a combi boiler. Water leaks out of the schrader valve of the internal expansion vessel. The water leaks when I take off the cap of the schrader valve and touch the value, just a trickle. Also the boiler hot water radiator circuit losses 0.4 bar pressure every ten days or so and needs topping up. Otherwise everything else OK. Pressure runs at 2.5 bar maximum

I am assuming that there is a leak in the expansion vessel membrane and I am assuming that the pressure loss over time is due to the leak in the expansion vessel

If I fit an external expansion vessel, how do I deal with the internal expansion vessel, as it will continue to leak.

Many thanks
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If the water doesnt leak out the current vessel when the cap is on the shreader then just fit external vessel if thats your plan and will be fine. If not sure then you can get a schreader valve core out of tyre place/halfords etc and replace it.
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Thanks for your replies

If I take the schrader cap off, it doesn't even drip really, it is just wet to touch. If I press the schrader valve and release some air I get some water with the air.

I have charged the expansion vessel up to just under a 1 Bar and I am going to keep an eye on the system pressure which is also about 1 Bar.

I will see if the system keeps pressure. If the system does not keep pressure, I guess it can't be due to the expansion vessel as no water drips out unless I touch the schrader value.

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