What is this part? It's part the boiler pump housing

[Deamon90002004]

Hey all, I have an ideal logic combi 35 boiler, it's about a 2010/2011 model, I have a leak from the back of the pump on what looks like a drain valve? I'm not going to mess with it, but it's so I know what to try and say to the company for when they come out. I shall include a picture showing the black nozzle I mean.
It only leaks when the boiler has been left to go cold

 

[oz-plumber]

It's a boiler drain point.
It may only need a nip up with a spanner.

Don't over tighten it - you may snap it off at the threads