Can a air tight tube be used to siphon water very high vertically as long as the end location is lower than the start? What is the limit that siphoning can be used for? For example, if I pre-filled tubing with water and then put one end in a pool at y=20 and the output at y=0 but the pipe had to climb over a 50 meter hill before it could decent to y=0 would the siphon effect still work. I ask because I know that a perfect vacuum has a very small upper limit on how high it can suck water up a tube (or have the atmosphere push water up a tube with no resistance). And I also know that siphoning works because the water resists forming a vacuum by "sucking" the water behind it until there is a steady stream. In my hypothetical situation with the 50 meter hill I tried to overcome the vacuum limitation by pre-filling all the pipe with water but I'm not sure if that would actually work. I can draw a picture if my question and hypothetical situation aren't clear.
 A: 
Can a air tight tube be used to siphon water very high vertically as long as the end location is lower than the start?

tl;dr: No, the water will spontaneously boil in the vacuum produced and since unlike nearly-incompressible liquid water, the vapor is a compressible fluid, it will no longer allow the siphon effect to continue.
Atmospheric pressure is roughly 76 cm of mercury, which has a density of about 13.5 times that of water, so we can estimate atmospheric pressure to be about 10.3 meters of water. When the pressure of water drops below its vapor pressure of 18 cm of mercury (or 0.24 meters of water) it will spontaneously begin to boil at room temperature. 
So if the high point of the tube is higher than about 10 meters and the tube remains open and doesn't collapse on itself, you will in effect be making something like a vacuum pump and the column of water will separate and establish a section of water vapor instead of liquid near the top.
If you raise the top higher, then you'll just get longer sections of vapor at the top.
Of course if your tube is not rigid enough to maintain a vacuum, it will instead just collapse on itself and tend to seal itself off. 
