On Mon, 08 Oct 2007 10:13:17 -0700, Keith Hughes
wrote:

...I proposed filling the tubes
completely with water so that the initial head space would be zero.

No, it won't be zero. It can't be. If it is, then you have a solid
liquid stream, and it's just a siphon.
....
A solid liquid loop will not separate into two separate columns.
....
Keith Hughes

Perhaps it would be better for you to check what is the maximal rise
(head) of a syphon. Can you guess what it might be?

Brian Whatcott Altus OK