how can i fix a leak to my baxi eco 80 boiler?

If it is leaking from the nut in question then the obvious solution is to replace aforementioned leaking nut
I would ring up baxi tech helpline to get an exact part numbet for that nut then i would recommend you shop around at local heating merchants for that particular part
If you do find the part the heating merchants could also offer you advise as to the level of difficulty in changing the part and might even suggest a local baxi speacialist who has extensive experience working on baxi boilers

Maxmad
November 2016