Drained off water pressure from my combi, attached an air pressure gauge to the schrader valve of the expansion vessel, it reads 0.4 bar - The boiler manual advises between 0.8 and 1.0 bar is the correct operating level. What are the possible causes for loss of air pressure? It appears to be a common problem with expansion vessels, irrespective of the boiler manufacturer (this one happens to be a remeha). Is it simply that the schrader valve has a relatively short lifespan? Diaphragm becomes weak with age? System topped up with too much water at some point, damaging the diaphragm?
They loose pressure overtime as the diaphragm is slightly air permable top up of air at service is quite normal but due to having to remove the boiler cover to gain access to the EV you should be Gas Safe Registered so wouldn't advise to do anything apart from contact a GSR boiler tech to repair
Cheers. Wasn't aware one had to be GS registered to get behind the cover! Oh well, too late now. Given how common this 'fault' appears to be on combi's, of any make, is it fair to say the EV is a wear and tear item in the same way a c/h pump or diverter valve seem to be? Boiler in question is 6 years old - is it perfectly reasonable for an EV to warrant replacing after that time?
Wouldn't replace unless blown but would top up every service The cover often forms part of the combustion seal therefore can affect the burn pattern/ emissions so comes under GS Also 6 years is about the life of a modern boiler from what we have found of late
Hi Haggar. A bit of doom and gloom there from our DNR . If you press the Sharder valve thingy and only air comes out, the chances are your diaphragm is perfectly fine and the air loss is as DNR says - permeating the rubber skin or possibly a slight leak from the Shrad. Or both. But that's a very slow loss over 6 years, and is perfectly normal. Once you pump it back up to around 1 bar - making sure the boiler pressure is kept at zero during this process by releasing more water if necessary - you then bring the system (water) side up to 1 bar as well. There is no reason why this shouldn't be fine for another 6 years... If you have drained a lot of water out, it might be worth taking the opportunity to add more inhibitor to your system. You can get 'injections' of concentrate that can be squeezed in a rad bleed screw. Very likely you only had to remove the front boiler cover - a large decorative panel - to get to the exp vessel, in which case you should have no concerns about the 'combustion seal' which usually applies to a separate panel further inside the boiler which encloses the burner and exchanger etc. My boiler is 12 years old and I haven't even had to top up the vessel's air pressure yet, and the system pressure only once, and that was a wee tweak. I have little in life to boast about, so there...
Thanks for the advice DA. Yesterday I drained fully, repressurized the EV to 1 bar (with a bicycle pump) then refilled the system to 1.5 bar. Only air exits the schrader valve when tested. Intention is to monitor the system pressure level over time. EV pressure issue was complicated by a disabled pressure gauge, which I also removed at the time to discover it was full of black crud. Anyway, cleaned it and reattached. All well so far...touch wood... Thanks for the inhibitor tip - next time I'll take the opportunity to add some.
Sounds like a system flush is needed to be fair x400 in the system for a month then full flush 3-4 fills and drains the refill last time with x100 to protect it. A clean system is an efficient system and less likely to require any repair see it as a system service that's overdue , folk get their boiler serviced but forget the rest of the system
Haggar, ok it ain't a biggie, but I personally don't see any reason to have the system pressure at much over 1bar. In fact one single bar is awesome. It doesn't make anything work any better, but chust adds a wee bit more unnecessary pressure for the system to cope with. Not a biggie, but no need to do it. All it can do it to hasten pressure loss - by a wee amount. A tiny amount. So not an issue. Barely worth me mentioning. But thought I might as well. But, hey.
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