Leaking auto air vent (was: leaking pressure valve)

[SmileyDan]

This morning, 5am, woke up to a drip, drip, drip... from our ceiling. Oh-oh. Went up into the loft and found this was the culprit:

Untitled

• SmileyDan
• 21 Dec 2014
• 1

This appears to be some sort of pressure relief valve. It says "10 bar" on the top. The water was leaking from the black screw at the top. When I closed it, the leak stopped. However, I was worried that if this was some sort of relief valve I might cause a problem by closing it, so I opened it a bit and wrapped with a cloth for now.

So:

• What is this thing called?
• Why might it be leaking?
• How does one fix it?

Some more context...

We have an open vented heating system and hot water system.

I don't know if this is a hot water pipe or a heating pipe.

This is situated about 30cm from a chimney which was still warm from last night's fire. Could this be causing expansion? The stove did run hot last night when I made a mistake in loading it and it went a bit berserk, but we have fires most nights.[/list]

 

[Tipper]

It's an automatic air vent and you need a new one.

(A quick fix while you are sorting out a replacement will be to shut the valve below it)

 

[SmileyDan]

Thanks. So closing the wheel tap below won't cause a build up of pressure?

I forgot to say: I also found another identical valve discarded next to the above... A common problem!?

 

[jason61c]

They're only about £4.

 

[StevieV1]

Its not a pressure release valve, it simply lets air out of your CH system. If you close the tap below, it just means the air in the system wont get out and you can bleed the rads instead until you get a new AAV.

 

[SmileyDan]

Thanks everyone.

Could the following be the cause?....

We had new heating controls added a couple of months ago. As part of this we had the system drained (by a plumber) so that some rads could be fitted with TRVs.

After the system was filled again, on first attempt, the heating wouldn't work because there was too much air in the system. The plumber did some more draining and then it worked.

However since then I've been bleeding air from one of our rads about every other week or so! And the rads have been making some noises when working.

Dunno if I'm stating the "bleeding" obvious but are these possibly related?

 

[SmileyDan]

btw I'll keep the references to "pressure relief valve" in case someone searches for this term...

 

[Dan Robinson]

btw I'll keep the references to "pressure relief valve" in case someone searches for this term...

Why? It has nothing to with a pressure relief valve.

You might as well change the reference to "chocolate cake recipe"

 

[SmileyDan]

Just so if another numpty searches for the same question.

I guess the keywords are in the posts anyway so...

 

[SmileyDan]

In case another numpty like me searches for the wrong thing. Well I suppose those keywords are in the post now so...