This has a greater volume of liquid in the long leg than it has in the short leg.
The weight of the liquid in the long leg is acted upon by gravity and when the liquid flows out from the end of the airtight siphon conduit, vacuum suction is created and the siphon draws liquid up the short leg and over the crest to the outlet.
A siphon must have a longer outlet leg below the short leg inlet elevation to allow the weight of the liquid in the longer leg to create suction which causes the siphoned liquid to flow down and out the siphon end.
It is a long bent pipe that is used to transfer liquid from a reservoir at a higher elevation to another reservoir at a lower level when the two reservoirs are separated by a hill or high-level ground as shown in the figure below.
Working Principle of Siphon:
The point C which is at the highest of the siphon is called a summit. As the point c is above the free surface of the water in the tank A, the pressure at C will be less than atmospheric pressure.
Theoretically, the pressure at c may be reduced to -10.3m of water, but in actual practice, this pressure is only -7.6m of water or 2.7m of water absolute.
If the pressure at c becomes less than 2.7m of water absolute, the dissolved air and other gases would come out from the water and collect at the summit.
The Flow of water will be obstructed.
Application or Uses of Siphon:
This is used in the following cases:
- To carry water from one reservoir to another reservoir separated by a hill or ridge.
- To take out the liquid from the tank which is not having any outlet.
- To empty a channel not provided with any outlet sluice.