Vaillant Turbomax242 E loosing pressure

3 Jan 2011
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United Kingdom
I have a Vaillant TurboMax 242E which has been losing pressure, I have re-pressurised the expansion vessel to 1 bar. However, it is still losing pressure and dripping water out of the small copper pipe on the outside wall. When I checked the expansion vessel it was only air that came out rather then any water. Is the next thing to replace the pressure release valve?

Was I correct to re-pressurize the expansion vessel to 1bar?
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The PRv is typically a metal/metal joint. Any debris can sit between the faces allowing an escape.

By all means replace it, but, are you quite sure the Plate Heat Exchanger is not pinholed and allowing mains cold water to enter the 'system' water and push the pressure up to 'blow-off' pressure, what pressure is the guage showing?

How would I check if Plate Heat Exchanger has been pinholed?

After re-filling the system the pressure was 0.9 Bar cold and about 1.5 Bar when it warmed up. However there is still water dripping out of the copper pipe so I suspect that the pressure will drop back off again.

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