How a siphon (syphon) works

Explanation of how a siphon (syphon) works, and why the pipe does not empty.
For technical explanation of how tank of water drives a flow for a pipe at the base of tank, see:
• Bernoulli's equation e...

[@fluidsexplained1901]

Check out new content on this channel about the flume I built in my office: kzbin.info/www/bejne/qaHTknWnpa6HY9k

[@stealthchopper54]

Thanks

[@austing9060]

Images go a long way when explaining anything relevant to math and science. For anything within the trades videos like this go milestones in understanding

[@cfisher2447]

the fuck is a level haitch?

[@you2tooyou2too]

@@cfisher2447 Standard British pronunciation of the 8th letter of the alphabet. ;-)

[@lukelittlejohn_]

Christ. Thank you! It took like 5 videos before I found this one that didn’t just say “and then the water is sucked out”. WHY is the water sucked out. Finally someone actually answered, thank you.

[@fluidsexplained1901]

Glad it was useful! And yes, searching on KZbin and not fining many good explanations is why I decided to make the video. Hoping to re-make it with some real models in the future in-line with my new content.

[@arpitkumar4525]

@@fluidsexplained1901 Yes. The Internet has gotten worse. Lots of trash. Thankfully we still have people like you ❤

[@fluidsexplained1901]

@@arpitkumar4525 Thanks for the encouragement :)

[@dillondonnelly1108]

Love this comment because I’m order for me to be interested and retain information, I need to know HOW and WHY things work. I can’t just know that they do

[@luwyiki]

Thanks for making this video, its finally one that actually explains why this happens. Really appreciate it. :]

[@fluidsexplained1901]

Thanks for the comment, glad it was helpful!

[@fluidsexplained1901]

I am currently working on a new hydraulics lesson series, using models and real world examples. The first part of the first lesson can be found here: kzbin.info/www/bejne/e4rZppd4mq2bjbM

[@Andrewlyticz]

Thanks for the physics refresher. Actually used it to drain a pool at home.

[@fluidsexplained1901]

Thanks for the comment, very glad it was useful!

[@a.foolsworth796]

Thank you from an apprentice plumber. Very much appreciated

[@skillybiskuit12]

I got absolutely blasted off some Zaza and looked this up thanks for the explanation

[@24kxriots30]

The za be putting you in full concentration mode watching this huh😂

[@skillybiskuit12]

@@24kxriots30 2 years later I must say this video inspired me to enroll in college for a physics degree and stop smoking and I’m almost done with it. Crazy how one little decision can effect your entire life

[@carlomabinibayo1284]

Very concise and the explanation is on point.

[@fluidsexplained1901]

Thanks!

[@AnkitKumar-di2sj]

Finally understood this. Thanks for the video!

[@fluidsexplained1901]

Glad it helped!

[@RiverReeves23]

That was so incredibly concise. Thanks man!

[@fluidsexplained1901]

Thanks!

[@dlsk07]

That pipe needs to reach to the bottom of the container to have the same pressure as the first container

[@fluidsexplained1901]

Hmm, that’s an interesting one. My argument would be that in theory, the liquid has the same total head at all points in the container, so the tube position in the container should be irrelevant (apart from that in real life, if the tube is near the surface, the syphon will stop as the container empties). If the tube is at the bottom of the container, yes, pressure is higher than if it was at the top, but if the tube is at the top (as I’ve drawn), elevation head is higher. The sum of pressure head and elevation head at any point in the container must be the same if we assume the tank is static prior to the syphon starting, and either of these heads can be converted into kinetic energy at the outlet interchangeably. If you work through the maths, the only variable that is accounted for in Bernoulli’s equation is the difference in elevation between the water surface of the container and the outlet. By the time the water has made its way through the syphon and to the bottom of the tube just before the outlet on the right, it will have the same pressure as the pic on the left, as the elevation head has been transformed into pressure head? It’s the principal explained in this video: kzbin.info/www/bejne/f3aaY6KmbNVsr7s

[@James-dz5vu]

@@fluidsexplained1901 Yes that's correct, good explanation. It would make more sense for the pipe to reach near the bottom, but the overall net force will be the same as at the top.

[@abidobby]

Than you for the wonderful explanation!!!

[@fluidsexplained1901]

Thanks for the comment!

[@Cj_08_]

Thanks from IND to UK ...

[@fluidsexplained1901]

Thanks for the comment!

[@swarajojha3033]

Thanks a lot. I love physics when i umderstand it. You did the job 👍

[@fluidsexplained1901]

Thanks for the comment! I also love that feeling which is why I made the channel, very happy if my video did the job :)

[@aek12]

YOu are creating a new education revolution

[@brianty6676]

Thanks mate. Great video.

[@jjspider22]

Gotta say I love how that ink follows that pen 🖊 at 1:50 very nice

[@hamster-wh3ws]

Fab explanation, thanks :)

[@AjeetKumar-hy7cq]

❤❤❤very nice sir ji

[@jamstawildman]

Nice explanation! One very minor point: the letter h is pronounced aitch- it doesn’t actually have an h at the start of itself.

[@nahom3427]

Wow!! What a useful comment, appreciate it mate!

[@kakashi-yu7ok]

no shit sherlock

[@PTacify]

How would you explain that silphons also work in vacuum?

[@markker2727]

water from my roof collects in a big ol drum. when the drum fills it just overflows and pools in the garden, which is surrounded by concrete. on the other side of the concrete is a storm drain. i put a pipe into the drum and routed it to the storm drain, but the distance is about 10 metres and it kind of sags before rising a little to get into the drain. will it work? is there a way to make it work if it doesnt? like having a longer pipe that goes further into the storm drain. i cant quite get my head around it...

[@Jacquemini]

I got drunk asf and had to know this thanks for the video

[@smotala11]

I understand what you have said but it appears the explanation does not explain why the outlet of the pipe needs to be at a level lower than the water level. (Or maybe I have missed something?)

[@fluidsexplained1901]

This is what give the pressure different that drives the flow. Because if the water level is higher on one sider of the pipe, it means the pressure is higher, which pushes the water through the pipe.

[@ammonirmonir2437]

Thank you very much, I mean it.

[@fluidsexplained1901]

Thanks for the comment, glad the video helped 😊

[@shivaji856]

Well explained.

[@fluidsexplained1901]

Thanks!

[@jeetsingh-bg7fz]

They all said how …..you said why ….well done

[@frenatfarms]

Nice.. Thank you

[@vascoamaralgrilo]

Thanks!

[@qie2iqee]

So basically pipe filled with liquid flow under glass of liquid then because of pressure liquid gets pushed up pipe down pipe?

[@dzuzr]

Brilliant.

[@fluidsexplained1901]

Thanks!

[@hemantbisnath1486]

I need your help please. I am trying to drain off some water from a flooded piece of land to an area that's about 1 foot higher. Can you recommend something please?

[@hunterz1x321]

What you’ll probably need is an actual pump. Depending on the elevation and location of the flooded land you might have a high water table. After you pump it out, you might have to get fill dirt (to level them out with watch other) in order to prevent further water pooling there.

[@hemantbisnath1486]

@@hunterz1x321 thanks.. I'm working on getting a pump

[@fluidsexplained1901]

As noted by @HUNTERZ1X, if the area you are moving the water to is above the surface of the water you want to move, a simple siphon would not work. However, I also made a video about basics principals of designing a pump system (link below). Although in the video the water surface of the tank is above the end of the pipe, the maths and principals would work exactly the same for the system you are discussing. It might help in working out what pump to go for. kzbin.info/www/bejne/fHi5cqCNhtqIntU

[@jayrashamiya2810]

Does this explain why it doesn't work when the height of outer pipe is higher than the height of water in the tank?

[@chrisdeep8417]

A good explanation but would disagree on a couple of points. Firstly the vacuum wouldn't need to be perfect. If you connected a transparent vacuum chamber at the top with a larger volume than the section of tubing you would see the water from the top bucket pulled (or more accurately, pushed) up, accumulate at the bottom of the vacuum chamber and flow back down again. The section of "air" at the top of the vacuum chamber would have to remain below 1 atm enough for the atm at the surface of the top bucket to push water into the chamber. The mass of the height of the column of water going to the bottom bucket (along with gravity) preserves the vacuum below 1 atm. The second point follows from the first in that the partial vacuum and water at the top section of the tube can be separated but this can never happen with just the tube itself but requires a separate break section with greater volume than the rest of the tube.

[@fluidsexplained1901]

Thanks for the comment, that’s really interesting! I actually made this video without thinking too much about it after one of my students asked me about a syphon. So in my mind, it is quite surface level explanation just to get the main concepts across. When I threw it together in a few spare moments, I could never have imagined that it would be my most popular video with more than 80K views (way more views than my more recent videos that took me a few months each to make)! I’ve also learnt more from well informed comments like this. Maybe there is a need to re-make a more comprehensive version some day!

[@S4R1N]

I still don't understand the definition of the "pressure" of the water that allows it to flow via a siphon. Is it correct to assume that the reason it continues to flow is purely because of the possibility of a vacuum that causes the exiting water to always drag the adjacent water out until equilibrium between the exterior environment and the environment at the point of entry to the siphon?

[@fluidsexplained1901]

Hi, thanks for the comment. Yes that’s correct. There is a pressure difference between the surface of the tank and the outlet pipe (at atmospheric pressure). So this pressure difference forces water through the pipe. The only thing that would stop the flow due to the net pressure difference between the tank and outlet would be if the water was to ‘fall’ back down the pipe. But this can’t happen due to the vacuum - if the water was to separate in the pipe, the volume where the water had separated would be a vacuum and would therefore have less pressure than the water on either side, so it would be immediately closed. Essentially the whole problem can be solved by the simple idea that water always flows from areas of high pressure to areas of low pressure. Hope that helps?

[@S4R1N]

​@@fluidsexplained1901 Awesome, thanks a lot for the reply! That's good, that fits with how I assumed it worked, just never really knew how to put it into words so thanks for the clarification!

[@warriorprincessharmony]

Yep. Exactly

[@triparadox.c]

I am here because the brief explanation of "how a bore evacuator works" just doesn't cut it for me.

[@ΗλίαςΦασουλάς-π8γ]

Well said

[@josephpostma1787]

What happens when the lengths of pipe boths before and after the bend vary?

[@supahbeebz]

mfr’s hitting pause in episode 4 trying to figure this shit out

[@artarealmblazer]

Lmao

[@tomwinkler294]

Isn’t the pressure at the bottom of the tank much higher than the pressure at the top of the tank? I would assume the pressure would not depend on the hight of the tank but rather just the hight until where the tube is inside the tank

[@anilkumarsharma8901]

Show how much energy we got by siphon at maximum level Stp and ntp Siphon under high or low pressure created more energy efficient???

[@সমুদ্রসন্তান]

Brilliant

[@Fadexpl]

I have a question; you repeatedly state that there has to be no air in the pipe. How does this relate to flying droplet siphons? There is clearly air inbetween two water pipes.

[@jamesbela9719]

Hi and thanks for the video, but I have a question. Let's imagine a straight pipe from the tank, with a turn at 90 °, then a straight horizontal section of pipe, another turn toward the bottom at 90 ° again, and finally a straight vertical section of the pipe. I made the hypothesis that at the initial condition, the fluid in the pipe is at rest. So, I calculate the pressure at the inlet of the pipe into the tank Pe = rho * g * (Za + H - Ze) + Pair (where Za is the free surface altitude, Ze the altitude of the inlet of the pipe, and H is the distance between the free surface and the highest point on the vertical straight section of pipe because, in my opinion, all that height of fluid weighs on the inlet ?). So, I used the Bernoulli law and calculate the condition for having an outlet speed > 0. The result is that Zs < Za + H (where Zs is the altitude of the outlet). Am I right? Because I have seen also in a video that the condition should be Zs < Za, with a classical flexible pipe. Thanks in advance.

[@Kybone]

Time to put theory to practice and figure it out

[@anilsharma-ev2my]

Please show how much workdone in joules One meter higher one meter cubic water volume tank siphoning by a pipe of one inch to ground tank Vise versa How much workdone required?

[@arsvacuum]

Thank you ❤️

[@fluidsexplained1901]

Thanks for the comment!

[@mikezin25]

Thank you so much

[@bryantrocio4423]

Hello.. I want to ask.. Can the water increase its pressure when u make an tube arc that ishigher. Imagine when 3 floors. 1st floor is the the outlet. 2nd floor is the water jug(source of water) And 3rd is the water arc of the water pipe We all know that we can directly get water from the source in the 2nd floor directly to the 1st floor.. The question is.. If we increase the height of the tupe upto the 3rd floor. It will increase?

[@fluidsexplained1901]

It’s a good question. The only parameter that sets the systems total pressure in the system, if the start and end are both open to atmosphere, is the difference in height between the start and the end point, regardless of how high the arc is. If you think about it, a water particle has to lose pressure to climb up the arc, and is then only re-ganging what was lost as it comes down. On the way up, pressure is being converted to potential energy, on the way down the opposite is happening. Hope that makes sense?

[@mikego2611]

So, syphons wouldn't work in vacuum?

[@Altro99088]

How to identify Britishers: wathaa!!

[@jamesgutierrez3144]

Is the height from one body of water to another the cause of the vacuum strength for the suction or is it gravity

[@fluidsexplained1901]

Both, the height is essentially potential energy because of gravity.

[@chrisdeep8417]

The density of water in the section of pipe going to the bottom bucket multiplied by its height is what determines the negative pressure or suction (hence it's both). Very similar to how a barometer works. So in principle if the tube was perfectly rigid this could lift the water up just under 10m (equal to 1atm) and back down again (minus the extra bit needed for the bottom basin).

[@m_gwb]

I'm only watching because literally every series of taskmaster they try this and no one has yet to succeed.

[@you2tooyou2too]

This is a very limited (only one) example of the many ways that siphons can be/are used: partial/inverted/self-starting/capillary/bubbling/barometer/... PS: 'vacuum' is nearly possible above about 32' (a function of barometric/atmospheric pressure), near which the water near the apex will be boiling and the column will collapse.

[@iggytse]

I just bought a jiggle siphon but couldn’t sustain the flow. Now I realise the hose needed to be filled first.

[@fluidsexplained1901]

Hope the video helped!

[@iggytse]

@@fluidsexplained1901 it help lead me in the right direction. I have discovered with this jiggle siphon it helps if the top container has a high water mark. There might be a way to get it to work with a lower water mark but haven’t tried it out yet. But the real test is to see if I can use the siphon to empty a flooded backyard while it is raining. Have to wait until the next big rain event.

[@frozenwaffles240]

AKA…Bernoulli’s Principal

[@harshagunasena2693]

super................

[@anilkumarsharma8901]

why siphone bell siphone and heron fountain become a perpetual source of energy by applyeing some little pressure or extra effort so we got more energy by applyeing littele energy since potential energy of atmosphere is never ending forever

[@abdulwahabalahmari3606]

you did not speak about siphon you spoke about placing the siphon pipe in top of the water tank what if we put the siphon in the same location of the first example? can we use the siphon as a valve when the pressure is high the water will go when the pressure is low the water will stay? you did not answer that and siphon has S-shaped you did not drew that

[@Dgoshy]

Water level “haiche”.

[@LakhsTsoyknikas]

[@kakashi-yu7ok]

how do we open the fuel tank of car with out vehicle key or without destroying the opening?

[@supriyosamanta511]

এটা বায়ু শূন্য স্থানে কাজ করে স্যার

[@mr.curious1537]

Actually Cohesive force also comes into action, as this air pressure theory is already debunked.

[@balchalbalchal]

How? Please share links

[@mr.curious1537]

@balchalbalchal, you find out yourself , you have full internet, try to work harder for just 5 minutes.

[@THE_FORESAKEN_GAURDIAN]

🙂

[@rajkumar02468]

I cant unterstand

[@jsmith2132]

Annoying .. keep your pen caps OFF !

[@charlesclarke4397]

Stop clicking the pen lids on and off its very annoying!

[@fluidsexplained1901]

Thanks for the feedback. All new content has the egregious annoying lid clicks edited out from Dec 2020 onwards. We live and learn…

[@Bellevue_hc]

Can’t have the markers dry out!

[@deandee8082]

pretty bad man, pretty bad

[@tyriqcleo5899]

This was actually a terrible presentation by any standard

[@fluidsexplained1901]

Hi, thanks for the comment. A lot of people have found my videos useful, but I appreciate not everyone will! All the best

[@ice9232]

Imma be honest with you, that's not really true