Combi boiler

[stuplumb]

Hello all, Underneath my combi boiler I have a leak of water coming from one of the valves that feed pipes into the combi. 1 valve has a black handle which is leaking water and the other valve has a red handle which appears to be ok. What are these 2 valves for? The black valve which is leaking feeds into a black pipe/housing and it is at this point where water is leaking out. Is this something I could try and tighten myself or is is time to get the gas safety chappie in? I work with copper pipes and high pressure solvent weld pipes so general replacing of valves, flanges etc is not a problem but I was wondering what these 2 pipes are for?
Thanks for your time.

 

[Rickster123]

Any chance of a pic of it stuplumb?

 

[Barry98]

or the make/model of boiler