OK .... here is another newbie question

I want to run an open wire feed to a 160M Dipole .... I need to bring
the feed in and across my basement. I want to run along the floor joists
but like most basements there are pipes and duct work all over.

What would be the minimal acceptable separation between other metal
object and the open wire feed???

For an idea of what I'm up against:
http://pabut.org/feedline.jpg

Thanks,

de ka2pbt