Can anyone identify this fitting?

E

extopia

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IMG_8655.webp


It is on the buffer tank of an underfloor heating system, and unfortunately it is leaking.
 
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It is a pressure relief valve and looks to be on top of a hot water tank or similar. If you've an electrical fault and the heating element goes on but doesn't go off the water can start to overheat. This valve allows steam or pressure out of the tank is a safe controlled way.

This one is old and failed and needs to be replaced. Newer ones can be connected to the waste. That way if you've a fault and pressure builds up steam or water start coming out they go straight out the drain.
 
On mobile (Android) I can click on the photo and choose Search image with Google Lens, it automatically selects the valve, and then gives me this...
AI Overview

The item in the image is an automatic air vent (also known as an auto air bleed valve) on top of a hot water cylinder or boiler. This component is used in heating systems to automatically release trapped air from the water, which can otherwise cause noise, reduce heating efficiency, and cause corrosion.
  • It has a red cap that is typically unscrewed slightly to allow air to escape.
  • The surrounding rust and corrosion suggest a potential leak or long-term moisture exposure around the valve's base, which may require inspection or replacement.
  • The larger red-handled valve in the background controls the flow in the copper piping.
  • Automatic air vents often contain a small float mechanism that opens a valve when air is present and closes it when water fills the chamber.
Click to expand...
 
Thanks. It’s part of an underfloor heating system, as mentioned above. Now if only I could get a plumber - it’s in a part of the country where they are in very short supply. Is a DIY job possible? Eg just replace the red plastic part and the rubber washer under it?
 
This looks to me like it's on top of a pressure vessel. The cylinder looks like it's in the background ( in blue) The red cap would normally be a little loose. The bladder may be gone in the PV . Is the pressure gauge on the boiler , ( or on nearby pipework) reading low? If there's a gate valve on the single pipe that enters the PV , then you could attempt DIY ( a plumber would be a better bet though ) . Not a great photo for context, but looks like a new PV needed.
 
IMG_8654.webp
Not a pressure vessel. As mentioned under the pic, it’s part of the heating system - a buffer tank to reduce cycling in the system. It’s about the size of a regular hot water cylinder but completely separate from the hot water system (not connected to the blue hot water cylinder in the background, just sharing space in a ‘hot press’ type area.

Wider pic above.
 
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Ok, I see that now. I'm not a plumber, but have a lot of experience in the domestic build/renovation/troubleshoot/ world.
Best bet is a plumber....in particular the one who installed the system if possible. If not, then the next best available one and have the auto air vent changed out.
If its last resort DiY then I suggest...There are 2 gate valves top right. One above the circulating pump and the other on the right of that again. With the system powered down, ( very important) they can be turned off to isolate the buffer tank. Changing the vent should be straightforward with the right tools.You'll get some water spillage. Be aware...sometimes stems on gate valves seize/snap , the air vent could bust or dethread and you're in deep doo-doo.
In short, it's a small job ( assuming no underlying systemic problem) but in your shoes it's one for a plumber , who'll be able to deal with anything that could go wrong.
Oh, and NEVER mess with water or heating after 12 o'clock on a Friday.
 
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