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Oct 28, 2017
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South West
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DIY or Homeowner
Hi everyone.

When I looked in the cupboard where our gas combi boiler is installed, I found a wee white plastic cap which had pretty much disintegrated. A search found it was the cap that's meant to seal off the flue test point - from which a nice breeze from outside was ensuing.

As it happened, I had fitted a CO alarm inside that cupboard as I thought that any flue leaks would show up in there first, and it has not gone off, so I guess this test outlet hasn't been allowing too much flue gas out?

Anyhoo, my question is - where can I find a replacement, please? I haven't found one for this specific boiler, but ones for other makes such as Vaillant look similar - are they identical? Oh yes, another Q, please - why does a tiny plastic cap which is clearly made from inadequate carp material cost in excess of £14?!

The boiler is around 14 years old, right enough, but does this suggest that other parts of the flue system are also disintegrating?!

SAM_0002 (2).JPG
 

I would advise you not to use the boiler until you have a new one fitted
 
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Reactions: DevsAd and Aquarius
Yes very similar, as they’re part of the same group (Vaillant/glow worm). Might not be the exact same cap though.
 
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Thank you both.

Yes, boiler turned off until new cap obtained.

It's a different style to the one you linked to, Gasmk1 - it looks like part number 0020031334 with the two raised circular ridges on the top - see photo below.

Do you reckon the actual thread sizes are similar so are interchangeable? Cheers.SAM_0002 (3).JPG
 
Thanks everyone.

I should go for the similar-looking (with raised ridges) 0020031334 rather than the flat-topped 0020020502?
 

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