AAVs - why do they fail so much?

[Bunker]

Almost every Grant I attend has a leaking AAV, this one is on a Firebird. Changing them doesn't fix it, what do you do?

 

[Mike Jackson]

Normally mucky system. Recommend system is flushed.

 

[phil the bucket]

If its a sealed system Usually to do with expansion vessel
Needs re charging or undersized

 

[Ermintrude]

Normally mucky system. Recommend system is flushed.

If you disassemble Aav once removed normally find that muck trapped between top of float and lid of chamber or guide for float is mucky, thus when air has left system Aav isn't reseating properly. Think most Aav are tested to. 10 bar so prv should kick in before it fails?

 

[Bunker]

Funnily enough, i posted the op while at work, the very next job was one of those 'services' where actually its a leak, kitchen roll soaking in base of boiler cab -

Custard: "can you fix while servicing?" -
Me: "No, lets fix the leak then see if there is time to service it..."
which there wasnt so they'll have to pay the call out.

Grant, another AAV - immediately after posting the above, how timely! Fortunately a gravity on a bungalow with idyllic loft access etc.

 

[Best]

Heat seems to ruin them & cause them to leak.
If they are on a colder part of system they tend to last & last.
Sadly can't do much when they are screwed straight into top of boilers, - unless somebody knows of better types.

 

[kimbo]

Vent air from system and then screw black plastic cap in. It wont leak then

 

[Ermintrude]

Vent air from system and then screw black plastic cap in. It wont leak then

Kinda eliminates the auto bit though?

 

[mountainman]

From a Turbomax yesterday.

 

[kimbo]

Kinda eliminates the auto bit though?

When the air is out its not needed