VAILLANT ECOTEC VUW PRO 24 28 EXPANSION VESSEL 181051

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It’s meant to be the grey zone is safe but the bottom of the grey zone is so much different to the top. If you have to keep repressurising your Vaillant boiler you should get that problem found and fixed as soon as possible. If your Vaillant boiler is losing pressure overnight you will have a leak somewhere on your heating system or the pressure relief valve is letting the water out.

Vaillant boilers are sometimes undersized when fitted and are not large enough to cope with a large house’s central heating system. You should see a schraeder valve on it - don't let the name panic you it looks just like the ones that you pump your car tyres up with Compatible with aroTHERM air-to-water heat pump hybrid system - Making the perfect entry into renewable systems If you need to repressurise your Vaillant boiler once or twice a year I wouldn’t worry about it as it’s such a small leak that it’s barely noticeable.This is most likely an expansion vessel problem, if so, you will need to recharge it or replace the expansion vessel if the diaphragm inside is split. If the bag is dry after your Vaillant boiler loses pressure overnight you must have a leak on the central heating system which will need to be found and fixed. If the expansion vessel diaphragm is faulty when the air valve is engaged then water should/will come out? Thank you so much everyone for your responses. I've read through the FAQ and it makes sense on the whole. I just have a couple of questions: However if the system is under pressure then my understanding is that of course water would come out of the air valve and the person doing the job is trying to con me into getting unnecessary work?

Another cause could be the expansion vessel has lost its air and needs to be recharged or replaced. Leave the drain off open and pop the front cover off the boiler. Now don't touch anything except for the red expansion vessel down the right hand side, looks kind of like a metal hot water bottle!!You should ensure the heating is turned off before repressurising the boiler as it will sometimes fire up as soon as it reaches the minimum working pressure.

Having been reading various threads here and from watching the boiler this morning I think I have gotten close to the problem.

Upgrading GCH to sealed system - Expansion Vessel Question

This means the expansion vessel on the Vaillant boiler might not be big enough and can cause problems with the pressure. Having the boiler pressure too high (above 1.5 when the system is cold), means you will need to let some pressure (water) out of the system. The system pressure kept going really high when the heating was on. But when the heating cooled down, the pressure went really low and caused an F22 fault. What Causes Boiler Pressure To Go Really High I'm no expert at all but from reading lots it points to the expansion vessel either needing a recharge or is failing/failed. I see that you can test the Schrader value for water. I also read that vessels last around 10 years, which if true means we're fairly close to it.