My boiler has an Emmeti auto air vent on the boiler - it was replaced at a service a few years ago. I noticed that the fitter left the dust cap on it.
I loosen it now and again - but don't like to leave it lose as it spits out hot water. Is this normal?
When I moved into the house new - I found that the original vent had a cap on it that was screwed down.
Logic tells me there shouldn't be a cap - but I am reluctant to leave it loose in case everything gets wet.
In article , John writes
It shouldn't be but apparently is, many claim that in hard water areas the float/valve assembly will crud up and cause sealing problems but in a sealed system I can't see it myself. I leave my own AAV caps open a crack (in a soft water area) and I haven't experienced a problem but expediency is the better part of valour, if they leak, close them down.
If everything was working in good order and the system pressure hold up OK then there is little risk in leaving the cap open.
Otherwise the cap is a great convenience when the auto aspect of the auto air vent fails.
to see it without a mirror and a torch so it could leak undetected.
I think I will keep loosening it every week to release any trapped air.
Auto air vents are for filling only and should be screwed up after commissioning. They are not meant to be permanently open.
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