Grant Vortex Pro Combi 26 - Gurgling Air noise on Direct Hot Water side.

4 Jan 2010
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United Kingdom
Hi All,

I have a Grant Vortex Pro Combi 26 which is generally performing well but has a strange problem with a gurgling/fizzing/knocking noise when the Direct Hot Water pump is circulating. The central heating side is all nice and quiet.

At first I thought the hot water was being over-heated as the noise seemed to get worse as the heat store was getting up to its temperature. However I later noticed that the noise would happen if a tap was run for about a minute and the burner wasn't even firing (just drawing heat from the store).

There is no air in the radiators and I do not get any air if I release the manual air vent. As far as I know the Automatic Air Valves are working - I've actually heard the one on top of the hot water store expel some air during one of the many hours I've spent listening to the strange noises!

It might be worth mentioning that the AAV on top of the hot water store looks like new but the other one has some greenish staining around the casing. However, I've inspected the air release hole and it is clear - I wonder if it leaked out a bit of water at some point..?

Also worth noting that some days it seems worse than others. Some days it just parps and fizzes and others there is a full on knocking which is quite worrying!

I saw a previous thread from years ago which seemed to detail the same/similar problem and Boilerman2 mentioned an issue with air being stuck in a non-return valve... I'd be keen to know some more information about that if this seems like the same sort of fault. I was unable to find any more information about that on the site.

Any help gratefully received!!
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Reliease the pressure and tak off all the aavs and slowly fill the boiler once it's all full replace all the aavs.Bob
Thanks Bob. Just to confirm, do you mean completely remove the AAVs and then put the old AAVs back on after filling?
Not sure of the logic in this approach.
If aav' are ok then why remove them ?
If they are fooked why replace them in boiler?
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It's just what I do cos sometimes aavs don't work properly and customers don't want to replace them but that's just me and my working it seems to work.Bob

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