Comment Re:Plot twist: (Score 1) 360
Yes, but siphon is not caused by that ambient pressure gradient. You can do a thought experiment to confirm that - assuming you've played with such equipment enough for an intuitive understanding.
Put the upper reservoir in a pressurized container, such that ambient pressure inside it is a little higher than atmospheric pressure at lower reservoir level. Put the lower reservoir in open, at atmospheric pressure. Try siphon.
Result - siphon still happens.
There is one more theoretical test you can do to show siphon is not caused by ambient pressure gradient - the fact that stuff flows from lower pressure to higher pressure.