Hi,
With a pressure difference of just one atmosphere, you can pump a vertical column of water to about 35 feet, or a column of mercury to 29.9 inches.
Gravity is definitely the motive force in the syphon, but the maximum working differential pressure of the "pump" (from surface of higher container to top of syphon tube) is limited to one atmosphere.
Last edited by rudderrudderrat; 11th May 2010 at 09:41.
Reason: typo