Baxi Combi 80e AAV O ring seal

14 Apr 2012
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United Kingdom
New to the forum and would appreciate some advice.

I may be going mad but where should the o ring seal for the automatic air vent be fitted. My AAV is leaking so I purchased Baxi part no 248043, the AAV, and also the associated o ring seal which is Baxi part no. 248044.

I can clearly see that the AAV is screw in but where is the o ring seal supposed to go as it is clearly too small to fit anywhere on the AAV itself!

Thanking you all in anticipation.
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I cannot exactly visualise your boiler but suspect it may be what I call a Puma with the AAV at the top left?

If that is so then the original AAV may have had a groove machined for a rubber ring. They are supplied with the ring. You may have been given a generic AAV instead.

Regardless, you will probably have to seal the thread with PTFE tape.


The O ring should be pushed over the threaded end of the AAV right up to the shoulder. It will stretch to fit. Some will wrap some ptfe on the thread as extra insurance. Not needed if the joint is clean. All should become clear once you remove the old valve.
If you got part 248043 AAV then it should fit.
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I can see that the replacement AAV is identical to the faulty one. There is a larger 1 1/2 inch o ring seal already up to the shoulder as you say. The o ring seal I refer to is a mere 3/4 inch in diameter and will not fit on the AAV even if you stretch it as far as possible? As previously mentioned, the part numbers are just one digit apart which would indicate that they belong together, but then again?

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