Danger, the system is not open to the environment other than to air through a very fine mesh screen. This is, I think, a real and hard hydrodynamics problem. Watch postings by FredGarvin.
I negected to mention to him that am morally certain the answer lies on the fact that you cannot siphon...
I do not know the answer to this problem, but I expect the simplest pipe shape I am interested in that would cause the original behavior at E would not have the cycles.
I really like this puzzle and think it would be a great problem for an advanced physics class.
This is a very curious situation.
I have a large water tank on the top of a hill.
It supplies a gravity fed water system that works fine.
There is an under ground pipe with one end A in the bottom of the tank.
The other end E is about 80 feet below A, and has a faucet.
None of the pipe is...