STOP THE PRESSES!
A new revelation! I was looking at the video again of the bubble test, and I noticed what looked like a particle lifting up. So I zoomed in and cropped it, and sure enough a particle of dirt in the line starts to lift up as the RPM is increased.
That means the tube has a low pressure, vacuum, SUCTION!


At the 12 second mark you can see it start to lift:
http://vimeo.com/12697462