Identify a central heating component please

[M123]

Hi

Can anyone identify what this is please?

It is located between the central heating pump out and the input to the boiler. Is it some type of old automatic bleeder valve?

It has quite a large spring with nut on top of it...

I ask this as there is still air in the system after a recent draining of the system and was wondering if this valve has become inoperative?

Erm, Can I undo the centre nut and try and loosen it? Or would there be a leak?

Thanks for your help in advance.

 

[SimonG]

Looks like an old spring loaded relief valve. I'd leave it alone.

 

[M123]

Thanks. How do these valves work? - what are they used for? Over water pressure? or to let out any air?

 

[SimonG]

Spring loaded, for over pressure situations.

 

[M123]

Great stuff many thanks mate

 

[stevetheplumber]

when it leaks,which it will eventually replace it with a plug