Automatic air vents in loft spaces: Questions

[WaterTight]

Do you use them? And if so how long would you leave one on a system that had air in it before returning to screw down/isolate (after hoping the air would have escaped in meantime)?

Get the impression some of them leak if left but don't know how common this is. Perhaps some of you leave them happily long term?

Or do they work quick enough that you can fit one, run the heating and just wait for it to vent and then screw down? Do you hear it vent/like does it make a noise like bleeding a rad?

Thanks

 

[Last Plumber]

I never use them on domestic systems.
They are notorious for leaking. Once a correctly installed system with good water quality is full, it shouldn't really need constant venting.
I would use manual air vents if there are high points that do require venting.

 

[snowhead]

I used to do Commercial systems, most had some AAVs, some had many AAVs fitted.
Didn't matter what make they were, most ended up leaking after a few years.

I wouldn't fit one on a domestic system unless it was in a garage / outhouse or somewhere it didn't matter too much.

 

[Scott_D]

Fit a valve under to isolate them.
Shut them down once the air is out

 

[WaterTight]

Fit a valve under to isolate them.
Shut them down once the air is out

It's a regular sized bungalow. Changed a rad and valves by creating a vacuum rather then draining down but got some air in as a result as all on drops. Got it all working but they then called back saying one rad (that was getting hot) now not getting hot. So thinking still bit of air in there. But all the rads and valves are old. Touched one and it leaked. Not been in loft yet but my plan was (if problem rad doesn't just need bleeding, and if there are not manual vents in loft) to maybe let off pressure, fit an autovent with a shut off valve below it, tell them to let things run for a day or two and then return and shut off valve once air gets out. Does that sound like a good plan or too likely to leak even after a couple of days?

 

[oz-plumber]

Bleed the panel to see if that fixes the problem.
If not switch off radiators close to the panel that doesn't work to push the airlock through.

I wouldn't cut in an auto air vent in the ceiling space on an old system if it only had 1 or 2 problem rads.

 

[WaterTight]

Yeah I sorted a similar problem on a different job by doing that the other day. This one though I reckon I'll have a bunch of leaking rad valves to change if I turn them all off. The first one I touched leaked immediately and they all look about the same age and many piped in a way that would make changing them a pain.

Why wouldn't cutting an auto air vent in the loft with a shut off valve below, leaving it to run for a day then coming back and isolating it be a bad idea? If it is fair enough, just not sure why
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I mean if it's near guaranteed to leak immediately or within 24 hours why do they sell them?

 

[Scott_D]

They tend to weep eventually.
do the rads have drain offs to blast some mains s pressure through

 

[WaterTight]

Can you do that on a sealed system? Have done on a vented before.
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Went back today. Got one of two rads that weren't getting hot by just attaching a hose to each valve and running into a bucket, could hear the air come through. Then topped up pressure again. Tried the second one but didn't get any air as far as I could tell, just good pressure water. One side of the rad does have a drain off though. If you let off some pressure, like dropped it down to zero bar, then hooked up some mains to the drain off one one side of the remaining problem rad, both valves open, then gave it some mains until it got back up to one bar....would that maybe work?

 

[mfgs]

The best way to clear the air is to shut down all the other radiators and just leave the one which isnt getting hot, open. I know you are worried about disturbing the valves and them leaking, if this does happen and they are wheelhead/lockshield valves then its normally just from the packing gland which can be nipped up to cure. Just explain the risk to the customer first.

 

[WaterTight]

Not worried, just annoyed. I've touched 4 and 3 leaked. Not had much luck with nipping up glands on rad valves. Works for me on stopcocks.

Yeah I expect I'll end up turning them all off to sort the last one and end up changing every fecking valve in the house too.

 

[oz-plumber]

Easy money as far as I am concerned.

 

[WaterTight]

One way to look at it!

 

[king of pipes]

No I wouldn't fit em it's a short term fix and they will leak eventually, you would be better to drain down change all the valves you then have control and can flush through with mains remove alot of the debris and improve the water quality, a couple of manual vents in the loft should clear the air at high level a good quality inhibitor should sort it sorry to say there are no short cuts . Kop

 

[WaterTight]

Supplementary thought/question:

If automatic air vents are so likely to leak after a short while, why don't the ones inside boilers do the same? Just better quality?

 

[king of pipes]

Supplementary thought/question:

If automatic air vents are so likely to leak after a short while, why don't the ones inside boilers do the same? Just better quality?

They do 😜 quite frequently especially on old dirty systems . Kop

 

[WaterTight]

Ah... Fair do's. Do they ever leak really badly, waterfall style?