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Tim JA
Tim JA, HVAC Technician
Category: HVAC
Satisfied Customers: 2330
Experience:  Owner at Self-employed
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The Caleffi valve is leaking water. It is the type with a

Customer Question

The Caleffi valve is leaking water. It is the type with a black appears to be allen key socket on one side. The water is leaking from the hole on top. There appears to be a thread inside this hole, but no grub screw to close off the valve. Unfortunately the installation does not have an isolation valve immediately below the valve. At the bottom of the valve is is just a plain compression coupling, i.e no valve. For an emergency can I get a screw to fit in the top hole to temporarily close off the valve?
JA: How long have you been dealing with this plumbing issue?
Customer: Just today, following a flushing and re-fill with inhibitor.
JA: How long has this been going on? What have you tried so far?
Customer: I need to stop the Caleffi valve leaking. Just started an hour or so ago.
JA: Anything else we should know to help you best?
Customer: It is leaking at the rate is about two or three drips/second.
Submitted: 1 year ago.
Category: HVAC
Expert:  Tim JA replied 1 year ago.

Good morning, welcome to the Technical section in JustAnswer; my name is ***** ***** I will help you today.

That's an automatic air vent. I'm not surprised that it started leaking after a drain and refill - that's what they're prone to doing. The cap is supposed to be loose, and can be closed off when needed, but your cap has clearly gone missing.

The best you can do is wrap a towel around the pipe below the valve, to absorb the water, and drape the towel into a big bowl or bucket. The leak will probably slow overnight, and you can get a new AAV in the morning. The following product will probably go straight on in place of yours - if it looks different, then attach a photo of yours.

AAV at Screwfix

You don't need to drain again - just let all the pressure off and then water won't come out when you uncouple the old AAV.

If you receive a phone call offer, please ignore it - these are system generated and outside my control. My understanding is that you won't be charged if there's no phone call.

Customer: replied 1 year ago.
Thank you Tim. We managed to stop the flow by cutting off the supply from the CH header tank. I drained down about a litre of water and the valve stopped leaking and I could then remove it. Will get a new one from Screwfix, hopefully tomorrow.Kind regards
Expert:  Tim JA replied 1 year ago.

Do you mean the supply to the F&E cistern? There should not be a valve on the cold feed between the F&E cistern and where the makeup water enters the system. If there is a valve then it should not be closed when the boiler is running.