Vaccum to Bleed Loop

[Nigel]

My current build I'm working on uses a case to house my PC and then a separate case for rads, pumps etc. I was wondering whether or not I could use a wet/dry vac to drain the loop as bleeding at the lowest point isn't a realistic option with this setup.
My major concern is that even with the res cap off I'll collapse tubing on my rad etc when I attempt to do this.'
Opinions/Experience?