Does water always flow downhill?
In a pipe or tube, water can flow up or down as long as it empties at a lower pressure or altitude (or combination) than it started. I can pump it uphill of course. If you look at a rapid in a river you will see many places that the water flows up over an rock and back down as some of the motion energy of the moving water is momentarily converted to potential energy. The net motion will always be from a higher energy to lower (typically higher altitude to lower altitude) in the absence of machinery and energy input.
