Vailant combi boiler loosing pressure periodically

macadonald · 4 Nov 2014

Hi guys,

Before I get an engineer over, our vailant which is about 3 yrs old is loosing pressure on and off. It can be as much as 3 weeks while away on holiday, but since we've been back and using central heating possibly once or twice a week.

Desperately hoping it's not under the floor on the ground floor. What's the best way to check if it,a loosing pressure in the boiler itself? Am I right thinking the expansion valve can leak? I assume the water must leave somewhere... Would it be out the condensing pipe?

Thanks

Kyle

jackthom · 4 Nov 2014

First thing to check is the pressure when the system is cold and then when it is hot.

If it shoots up from around 1bar when cold to well over 2bar when hot there's a problem with the expansion vessel and you may be losing water through the pressure relief valve.

macadonald · 4 Nov 2014

Thanks I'll do that. I don't have a digital pressure gauge, it's just a fuel gauge type thing. I assume I can look for a pressure increase on that.

If the expansion vessel is a problem, where would the water be lost through? The same pipe as the condensation leaves from? It must be a fair amount of water...

macadonald · 4 Nov 2014

Okay, just run the test described above. Pressure definitely increased, but as it's not a digital pressure gauge, I can't be certain how much it's increased by. Still in the mid grey section...

I feel I need to locate any lost water if that's possible?

Bunnyman · 6 Nov 2014

If it is only 3 years old u do have a digital pressure gauge, press and hold the minus button for 5 seconds , the display will then show pressure

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Vailant combi boiler loosing pressure periodically

macadonald

jackthom

macadonald

macadonald

Bunnyman

DIYnot Local

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