Do Siphons Really Suck?

The fundamental forces involved in a siphon have been a topic of debate for many years. In the past, it was believed that atmospheric pressure is the main force which pushes fluid flow in a siphon and that a siphon cannot “suck” fluid without the aid of atmospheric pressure. However, a recent publication from The School of Chemistry at The University of Nottingham has proven this general belief wrong. Here is a picture of the abstract of the publication.


Click Here for the full publication. If you do not have access to this publication or do not want to spend the time to read it, I recommend watching this video from our Friends at Periodic Videos. This study found that siphons really do suck (a negative pressure is obtained from Bernoulli’s equation) and this is proven by siphoning fluid in a vacuum. The results of this simple experiment are so important than even the Oxford English Dictionary had to fix the definition of the word “Siphon” that they used since the early 1900’s. The study suggests that molecular cohesion and gravity are the main contributing forces for a siphon to work.


Boatwright, A., L., Puttick, S., Licence, P., 2011, “Can a Siphon Work In Vacuo?”, Journal of Chemical Education,88 (11), pp. 1547-1550.