vaillant vcw combi

28 Jan 2012
Reaction score
United Kingdom
Hi There,

I have recently noticed that water is leaking from the pressure relief valve.

If I top up the system and continue to run the heating , the pressure increases just above 2 bar and starts dripping from the pressure relief valve again until the pressure drops below 1 bar.

Is this a faulty expansion vessel or pressure relief valve?

Thanks in advance.
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Sounds like a bit of both. The PTV shouldn't open 'til around 3 bar but the pressure shouldn't be rising that much. It's possible that continual opening due to the pressure vessel fault has damaged the seating.

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