Vokera 28 Compact isolation

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I have rapid pressure drops in my boiler when the central heating is off and am trying to narrow down the problem.

I recently had new radiators and pipe work installed and I’m concerned that it could be a leak in the pipework or radiators somewhere, or potentially the boiler. I’d like to isolate the boiler from the radiators if possible to check if the pressure drops when they are not connected. Is this possible by turning the stopcock on the boiler off or some other way?
 
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There are flow and return isolation valves on your boiler but they may leak if you close them, what pressure does the boiler guage read when the heating has been on for a while ?
 
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Stays pretty stable when it’s on, so won’t really go up or down from 1.5 when its been refilled until it’s off for a period of time. It would normally drop to 0 after 4 or 5 hours of being off
 
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Thats fine was just checking your expansion vessel, there is a small copper pipe that will go outside from your boiler, identify it and connect a ballon or freezer bag or something to it and go back when the pressure has dropped and see if there is any water in it, could be that whoever fitted the rads drained your system using that and it could be passing
 
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Definitely got a leak ,most likely on system ,but tie a plastic bag over the PRV pipe outside ( copper pipe sticking out the wall externally) see if water collects in it.

Ian types a lot quicker than me :p
 
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So the bag stayed on the pipe overnight while the pressure dropped but there was only a tiny drop of water in the bag this morning.

Went down under the floor this morning looking for any sign of water but nothing there either. From checking the heater exchanger this morning it seems pretty corrupt and damaged at parts. Could this be the problem?
 

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First of all you shouldnt have opened the combustion cover but too late now, the heat exxchanger could be leaking, but normally the insulation pads are a lot worse than yours post a pic from further back showing the complete inside including the bottom of the combustion chamber, there shouldnt have been any water whatsoever from the PRV what are you calling a little ?
 
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When I say a little I mean I couldn’t see any water in the bag but could just about barely feel a drop in it. Maybe just condensation?

didn’t realise I shouldn’t have opened it but it’s closed now and here’s a couple of pictures I took
 

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wanted to see the bottom of the combustion chamber, dont think your heat exchanger is leaking but it could be, normally I would expect to see a lot more damage if it was
 
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Found these other pictures.

Can’t find any water near the boiler anywhere but whenever I fill it it’s rapidly going down! Tried going round all my radiators with some tissue to look for water but nothing showing up
 

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Vokera make many boilers and call them all compacts for some infuriating reason, for future ref yours is a compact standard efficiency, with a Bi_thermal heat exchanger, which looks as if it has been replaced, doesnt look like the boiler is the source of your leak
 
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Thanks Ian

I guess it's back under the floor I go to look for leaks! if I'm losing 1 to 1.5 bar in around 4/5 hours I should see a drip of some sort, right?
 
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There is a little trick that some of us use, sometimes works, pour some cheap perfume or after shave into the system water and you should be able to smell it near where the leak is, dont be tempted to use leak sealer
 
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