How Does A Siphon Work?

Have you ever emptied a massive container of liquid? Let’s say, for example, you own an above-ground swimming pool. At the autumn onset, leaves start falling and filling up any open and deep space close to the trees. Hence, it is probably the right time to prepare your pool for the winter by emptying it. If there is no drain in your pool, you might have to use a bucket for emptying it. That would take a lot of time. Why not bring science to your rescue and try siphoning the water out?

If you have ever brought a siphon to use, you are already aware that you need some time and a regular garden hose to empty the pool. If you don’t know how it works, do not worry. It is pretty straightforward. Just take your hose and put its one end in the pool. Place its other end outside your pool. Ensure this end is below the pool’s water level and to a region where you need all the water to drain. You can even use your mouth or a small pump for sucking water from the hose for starting the flow of water. After the siphon begins to work, it will drain the water out of the pool. It will continue until all the water is drained or you have lifted one end of your hose above the water level to make the siphon stop.

A basic siphon has a tube in a bigger container that moves up towards the edge of that container over a hump for emptying it in a container placed at a lower level. When the tube placed on the hump sucks the liquid and start emptying it into another container, it results in a decreased atmospheric pressure at the highest point of the tube where it moves over the hump. This decrease causes the atmospheric pressure over the liquid’s surface to push the liquid up in the tube at the region of lower pressure.

The usage of siphons goes back to ancient Egypt. As per the tracings found by historians, ancient Egyptians utilized siphons in their agricultural practices. These helped them in transferring water to irrigation channels from the canals. Today’s cotton farmers still similarly use siphons for helping in crop irrigation. Ancient Egyptians, as well as people in today’s time, also use siphons in the process of winemaking. Siphons help in transferring the wine from a big container to a smaller one. For this, the siphon is placed in the center of the container to allow more wine purity. This happens by discarding particles that floated on the top or moved down of the container.

If you are using a siphon for the first time, you’d think it is no less than magic. However, all this is just the principles of science doing their work. It is essential to understand that we do not really know exactly which principles are to be thanked. It has been a topic of debate for a long time. Although siphons have been in use for hundreds of decades, modern-day scientists are still debating exactly the forces that make siphons work. We look back at scientific history; the force of atmospheric pressure has been credited by the scientists for making siphons work. While the theory of atmospheric pressure mentioned above does make sense, some scientists have noticed this process needs air. A siphon, when tested inside a vacuum, still worked. Hence, it seems that there is another force also, which is at work here. More recently, scientists studying siphons have come up with a theory that makes gravity the primary power making siphons work. When the tube sucks the liquid over the hump, gravity uses its force and pulls the tube’s fluid. It is theory dependent on liquid cohesion.

Hence, the liquid must have the presence of an unbreakable chain of some cohesive bonds. Some scientists call it the chain model, as one can consider the water as a chain being pulled across the tube in place of the liquid. If you start pulling the chain through that tube and move it over the hump, the force of gravity will do its job and would continue drawing the entire length of that chain across the tube. Sadly, all the liquids don’t need to have strong, cohesive bonds for making them function in this way. Some scientists have created carbon dioxide gas siphons and flying droplet siphon with gas bubbles existing between the liquid molecules.

If you are already confused, let’s put it in simpler words. It might be the liquid cohesion, atmospheric pressure, and gravity working together to make a siphon function the way it does. Siphons are still being studied by scientists worldwide, and once they figure out exactly which principles are at play here, the mystery would be solved in no time.

The term ‘self-siphon’ comes into use in a couple of ways. Liquids that consist of long polymers have the ability to “self-siphon”. Such liquids do not have to rely on atmospheric pressure. This process is known as a tubeless siphon. A self-siphoning polymer liquid works in the same way as a siphon-chain model. The model is the lower part of that chain that pulls the remainder of the chain upwards and over its crest. Siphon manufacturers also use the term “self-siphon” in sales literature to talk of portable siphons that come with a pump. In the presence of a siphon, a person’s mouth or lungs or any other such external force is not required to make the siphon work. It is what makes the device a “self-siphon”.