Hi Folks,

After chatting with a plumber friend I know about an Auto Air Valve I have next to our boiler int he loft, I was surprised when he said those things always leak.

The Caleffi ones have a five year warranty but having googled it, seems failure is common. Are there better AAVs out there that have a long lifespan?

On another note, my system boiler has one built in too and that incidentally sits higher than the AAV which is on the feed to the coil on our UVC so I am wondering if it is even needed.

Thanks.

2 minutes ago, steveoelliott said:

Hi Folks,

After chatting with a plumber friend I know about an Auto Air Valve I have next to our boiler int he loft, I was surprised when he said those things always leak.

The Caleffi ones have a five year warranty but having googled it, seems failure is common. Are there better AAVs out there that have a long lifespan?

On another note, my system boiler has one built in too and that incidentally sits higher than the AAV which is on the feed to the coil on our UVC so I am wondering if it is even needed.

Thanks.

One is needed at each ‘high point’ of the system, where air gets trapped.

These are notorious for leaking (weeping) over time, but a clean healthy system will avoid early failure of these things (and many more).

Fit a full bore isolation valve under each one in your plumbing arrangement, so that changing these is appx a 5 min job with no need to drain the system at all then.

Weeping AAVs are usually down to dirt or magnetite fouling the float valve, or the system being topped up with fresh water now and then, which brings in more air and debris. They aren't doomed to leak, but the cheap ones do it far more often.

A few things that help:

Fit each one on an isolating or check valve, as Nick says, so it's a two minute swap without draining down.

Buy a decent brass unit rather than the cheapest. Spirotech's Spirotop has a good name for lasting, and Caleffi do a hygroscopic safety cap that swells and seals the vent if it ever weeps.

Keep the water clean with a magnetic filter and inhibitor at the right dose.

If air keeps coming back, a microbubble air separator on the flow clears dissolved air, and then the AAV hardly ever needs to open.

On whether you need it: air collects at local high spots, not just the highest point in the system. If the pipe to the cylinder coil rises up to that AAV and then drops away, I'd keep it, because the boiler's own vent won't clear air sitting in that hump. If the run falls steadily from the boiler all the way to the coil, it's doing very little, but it's cheap insurance either way.