What is this ?

[Darren E]

Guys, can anyone tell me what this is? They are like bike dust caps , would they be pressure release valves ?

 

[omega015]

air vents to allow trapped air to escape out of the system

http://www.screwfix.com/p/bottle-air-vent-15mm/34359

 

[Darren E]

That's great thanx, there was water coming out through mine, both caps were loose

 

[omega015]

Closing those caps means air cannot automatically be let out, its likely you need to clean/repair the vents or replace. The caps are there to manually stop water coming out when the vent fails to automatically close. Can you take a close up picture of just below the vents where they connect to the copper pipe.

 

[AGAS]

do not clean them , replace them

 

[ianmcd]

they are not expensive just replace them, the reason @omega015 is asking you to post a pic of where they connect to the copper pipes is so he can advise you what size you need to order

 

[Darren E]

Both caps leaking water when heating is.on

 

[AGAS]

Drain down and replace them if I was you, unscrew the brass section , there only a couple of quid

 

[terryplumb]

as already advised ,replace them .if it bothers you in the time before you can get around to doing it ,take the cap off ,wrap some PTFE tape on the thread and put the cap back on. this will stop water coming out .of course it will also stop venting air ,but OK for a few days