After I noticed your answer I looked again and I just found this:
So apparently (from the label),
(I can't speak Russian but it's writen "22.3*29.3*3.5" and it works: 22.3+3.5*2=29.3)
My water pump is leaking at the junction with the pipe behind it.
Apparently it's just an o-ring to replace and if I am not wrong it's the part labelled 210492J200
Does anyone know this oring dimension please?
I may ask to a Nissan dealer for one but I don't know if they will...