LOGIC COMBI 24 EXTERNAL PIPE LEAKING

[Monkeyking118]

Hi all,

Boiler has been losing pressure for overnight for a couple of days. Was at a loss, but have just found this on the pipe loop outside of the house in line with where the boiler is sited. What is its purpose?
Second pic is where I presume the pipe comes from. It connects to the very Last set of six pipes from the boiler (RHS as you look at it)

Any help greatly appreciated

 

[ShaunCorbs]

It’s a safety valve have you over pressurised the system ?

either way need a pro out to have a look