Inside a urinal auto-syphon.

I've always wondered what's inside the syphon assemblies used to flush the urinals in UK public toilets on a regular basis. I thought it would be a simple syphon with a pipe up the middle and an outer dome, but it's MUCH more complicated than that.
The mrmattandmrchay channel has done an epic video reverse engineering this syphon to work out how it manages to initiate a high volume syphon with very low water fill speed.
• The AUTO SYPHON cut op...
This device must have other applications too. From providing splashes of water in water-play areas to ebb and tide style hydroponic systems.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random plumbing accessories for disassembly at:-
www.bigclive.co...

[@craigshelley1663]

The primary siphon provides the main flow of water. Except that the bore is too large for a trickle to initiate the siphon. The large cup in the lower chamber forms a u-bend trap which creates an air lock in the primary siphon. The air pressure holds down the water level in the primary siphon. As the air bubbles through the trap it guarantees a swift start when the water level jumps up. The thin tube is required to provide a swift stop at the end of the flush as it is uncovered by the falling water level. It also prevents prolonged slurping sounds as air is drawn into the siphon. During refill, the effect of the air lock caused by the trap is inhibited until the end of the copper pipe is beneath the water line. During the flush the top plastic cup will be filled with water which will siphon into the u-bend trap at the end of the flush to ensure sufficient water remains to cause an air lock on the next cycle. Also, at the end of the flush, the copper tube provides an air path that helps prevent the u-bend from being sucked dry. This is a fascinating contraption. I had always assumed them to function as you initially described, but once upon a time my attempts to make a water clock with tanks representing hours and minutes was unreliable due to this trickle feed problem. Thanks for posting.

[@davedaniel2091]

Craig Shelley. How funny, I've just ended up here because I'm designing a water clock that will self drain when full...

[@Rac00n]

Craig Shelley holy shit that’s quite neet. Never thought that a complex mechanism like that would work wit such simple components

[@jdgower1]

@@Steven_Rowe Everything that is "sophisticated" or "complex" is based on simple concepts that are stacked one upon another. Even DNA is just made of four basic components, but codes for everything from algae to Blue Whales to Humans and Bacteria. Also, for the members of Nickleback and Five Finger Death Punch - but that's most likely due to a random mutation of the associated genomes involved...

[@jeffwells641]

@@Steven_Rowe No dummy, Plumlayers lay plums. So silly.

[@jeffwells641]

@@Steven_Rowe Ironic. [The Joke] [Your Head]

[@BEdmonson85]

It's funny how i can watch a video that explains nothing yet i learn so much. Keep 'em coming clive.

[@ThingsWhichArentWork]

Hi Clive. The little pipe going up to the top is to allow air IN to the top of the bell after the water level has dropped in the cistern - One of the problems with bell syphons is failure to stop syphoning when the cistern is emptied because the cistern is also attempting to fill at the same time. Having this pipe thin pipe up to the top of the bell allows the bell to fill with air when the water level drops low enough in the cistern, and that in turn breaks the syphon, allowing the cistern to refill properly.

[@Feyangel23]

Jim Conner you're goddamn right

[@Nilguiri]

I made a similar syphon for a homemade automatic indoor irrigation system made out of 2 litre coke bottles and PVC tubes and it sometimes has the problem that it fails to stop syphoning after it has dumped its water. I'll have to modify it for next summer's attempt. Thanks.

[@richlaue]

That is also my thought the pipe is used to break the siphon. Sometimes they have this in hydroponics

[@TerryClarkAccordioncrazy]

One of these was replaced at a place I used to work and we took it apart in the lab to try to figure it out and reached the same stage of confusion as you. The thing sat on the bench for anyone who passed by to have a go at understanding it and nobody managed it. As you say, stunningly perplexing devices.

[@twism666]

Wow, this deserves a follow up video after you find out how it works. Never thought I would find things like this interesting

[@davidcoghill8612]

My understanding of this is that the big pipe is just too big to auto-siphon on it's own, if left it would just trickle. So instead you have the big cup assembly on the bottom which creates an airlock and prevents any water from flowing through. The second plastic siphon sits higher up than the main pipe, once this fills with water, it lets water into the lower cup, once the lower cup is filled then the main pipe will start to flow. I think the copper pipe is there for redundancy. Toilet cisterns tend to fill up with sludge over time, a mix of scale out of the water and algae. If the smaller siphon at the top gets blocked, the water will get high enough to trigger the copper pipe to siphon instead. Copper is chosen as the material for this part because algae and bacteria don't grow on it, if the plastic pipe gets blocked up, the copper pipe will definitely be clear. (The design probably also aims for this copper pipe to have enough suction force when it siphons, to clear the blockage out of the plastic parts.)

[@bolton368]

I Imagen as the systen emptys the little breather pipe is exposed stopping the syphon ;)

[@100tjl]

Only thing I might add is plastic and metal hard vs soft water? the system back washes build up to pipe in takes sort of self cleaning?

[@DustinRodriguez1_0]

Ah, thank you! My main question was why they included an expensive copper pipe. I couldn't see any reason why it couldn't be plastic as well, but I could see it being antimicrobial. I had also been wondering if maybe the complicated design was due to needing to deal with clogging. Dimwits drop things in public urinals, and I imagine any design would need to deal with that.

[@GeneralPurposeVehicl]

I noticed one of the holes misses the cup entirely.

[@PWingert1966]

MIssing the hole is a personal problem mainly encountered by men when the lights are off.

[@swallin19]

The outer casing and the main outlet is the basic syphon, which is broken by air entering the small pipe into the dome. The other syphons are there to stop a powerful initial flow, causing a small flow to start, then increase to the max flow, till the sudden stop when the air pipe is exposed as the tank level stops, If they were not there, then the powerful surge would spray water out in the urinal nozzle, giving wet trousers! (assuming it feeds a stand up male urinal) With the soft start it gives a warning to expect a bigger flush is coming............ I believe the correct name is a cascade syphon for this type........

[@swallin19]

As always the exact operation of each part is more complex, with the holes in the chambers called seep holes that allow water in to ensure the right amount of trapped air in each syphon stage as it fills up. The multiple stages are also there to ensure a start will occur as well as preventing a rush. They also stop a dribble flush from occurring all the time

[@paulgascoigne5343]

the lower syphon cup cannot trigger the siphoning action of the main tube by itself, think about when you fill a glass up whilst underwater and turn it upside down and lift it so the rim in still submerged and you have a column of water. this is because, as you say, a trickle of water would keep trickling. so the upper smaller siphon activates when the level is sufficient, this drains into the lower cup, raising the level to flow over the rim of the lower cup - this breaks the stalemate meaning the main flow/flush can begin. The copper tube drains the upper cup at the end of the flush so it fully empties enabling it to reset at the end. the holes on the top cup enable it to fill and displace air into the dome, the other tube leading to the bottom of the dome allows the air to release otherwise water cannot fill it, remember the water is acting like a piston and would compress the air but without it the pressure of the air would balance with the water pressure and it would only half fill. That's my understanding :-D

[@paulgascoigne5343]

think of it like a couple of transistors switching a charge stored on a capacitor using a low voltage trigger with a reset circuit once the current drops below a threshold, enabling the capacitor to recharge under a low trickle. you don't want the capacitor to discharge until it reaches full capacity.

[@wilhobbs207]

Paul Gascoigne Sort of but you missed something. Check out my post above. :-)

[@MrNubix]

Paul Gascoigne great explanation, thank you

[@BigClive]

It sounds the most plausible yet.

[@hellterminator]

Unless I'm missing something, that can't be how it works. The way I understand this setup, that part is analogous to using a funnel to fill a bottle (liquid coming in from above the brim of a container through a tube that ends bellow the brim). If it worked the way you're describing it, it would be impossible to overfill a bottle using a funnel (yet, as we all probably know from experience, that can happen very easily).

[@lettucefire]

It's a russian syphon doll

[@Sci-Fi-Hooligan]

Beat me to it!

[@HarryL2020]

lettucefire haha

[@RFC3514]

Is that a euphemism for a mail order bride that empties your bank account?

[@katelibby713]

RFC3514 best comment award

[@stridermt2k]

LOL

[@SiskinOnUTube]

It's harder to start a large diameter siphon. I expect each stage dumps into the one below, to ensure that they start to siphon and don't just trickle. It's making me think of a Darlington pair, but with water.

[@JJayzX]

Trumped Up Trickle Down Fluid Dynamics

[@Falcrist]

Did you just mix electrical engineering and fluid dynamics? Get out. Now.

[@shadowwalker23901]

I would also like to note, that the smaller tube that that he says "is to let air out" is actually the complete opposite. It is there to help break/stop the siphon when the water runs down.

[@myopicthunder]

Why its easier to understand electricity by using the water in a pipe analogy anyway.

[@Falcrist]

Will Patterson It is easier to understand basic electrical circuits that way, but it doesn't work when you start dealing with second order field effects. Then you need to dip into Maxwell's Equations.

[@mrmattandmrchay]

I've worked it out, but I HAD TO CUT ONE IN HALF and put a PERSPEX VIEWING PANEL to see it working!! I went to a lot of effort to get to the bottom of it (I have plenty of footage) and it is quite amazing seeing the whole thing working! The copper pipe is the activator and starts the whole sequence when it creates a mini-syphon, then the bit at 8:25 (the cup within the cup) is an airlock which opens up as soon as the mini-syphon has started, allowing air trapped at the top of the unit to escape to bring the water level up suddenly, the water level inside now towers over the main outlet pipe and the main syphon is instantly started (i.e. a gentle 'trickle' won't start a major syphon). Just wondered if you received my email and the pictures I sent you?

[@BigClive]

Did you send it to [e-mail] ?

[@mrmattandmrchay]

@@BigClive Hi, I believe so, but I'll check and send it again. Thanks! Just checked, sent it to 'bigclive.1' - corrected now and resent.

[@LakeNipissing]

Install some colored LEDs in the various stages so you can see the liquid levels in them, and then re-seal it and set it up in a test rig to watch it work. Food color may or may not help with seeing the levels in the siphon stages.

[@llhand]

Or just drill or cut some holes in the places you want to observe and seal them up with with clear tape windows.

[@Sim0n98]

Are you sure it isn't another Poundland sex toy?

[@misterhat5823]

No. It doesn't have a USB port like the butthole warmer Clive took apart.

[@JangoBunBun]

Mister Hat needs to spritz lubricant as well, don't forget

[@richbooth8948]

It's alien body fluid technology. A liberal application of hot melt glue to cover your Dremmel work, a 5 gallon pail and some different food coloring would help you figure it out. The little plastic tube that attaches to the dome lets air in when the water gets low to break the siphon. The top little siphon arrangement is to bleed water out in case the main siphon fails for some reason, this preventing an overflow.

[@sparkyprojects]

I've seen urinals that have a slow flow for a while before the main flush starts, I'm guessing the lower cup fills and overflows, water still rises until the top cup fills to seal off the air coming back up the outlet, The small flexible pipe in the side of the dome is a vacuum break once the water drops below that level

[@rarbiart]

this devices totally lacks an USB connector and a shitty transformer with bad isolation.

[@MrThomasisashit]

Why do i enjoy these breakdowns so much? Your a legend Clive.

[@AximVidya]

I love how he has no issues explaining what each part in some quite complicated bit of circuitry does, but is completely stumped by some plastic tubing with no moving parts.

[@ClosetYeti]

6:13 Searching for the patents might be useful here as many patents also include images showing operation. Nothing quite like seeing it live, but it at least gives you an idea

[@williefleete]

So that's how those obnoxious urinals flushed. I always thought they were on some sort of electronic timer

[@nathanlucas6465]

william fleete these things used to work just on water continuously dripping in. These days there are electronic devices that control the flow of water into the cistern (cistermiser type devices) that can be a timer, a pir sensor or a water pressure change sensor, but they still use an auto syphon to dump out the water into the urinal

[@williefleete]

Nathan Lucas when I was at primary/intermediate school and the older buildings in high school it would have been the water siphon type, used to hate the sound of the things flushing so suddenly

[@ikonix360]

william fleete interesting. over here in the USA we either use a valve that is actuated by hand and let's some water flow then shuts off or we use an electronic valve that does the same thing.

[@joinedupjon]

+jmcinvale I've seen and been amazed by them... also quite often used in Germany too I think. fwiw I think british plumbing standardised on much narrower pipes coming up from the underground main for most commercial and domestic properties and you wouldn't get sufficient flow to flush anything properly unless you saved it up in a tank and then syphoned it down a wide pipe.

[@pileofstuff]

+jmcinvale: they used to be common in North America too. Stadiums, arenas and other multi-urinal installations. Most have been replaced in modern decades by the technology you describe.

[@ASilentS]

It's siphons all the way down bro!

[@MadCatmkII]

SilentS You got there before me. +1

[@MalleusSemperVictor]

The universe is just a siphon, in a siphon, being siphoned by another siphon, which resides in yet another siphon.

[@asmrwatchy]

You know you watch too much big clive when you already know its his video when you refresh the page quickly and go "Jesus christ what has Clive bought now"

[@mursie100]

I watch videos of Quantum Mechanics, Special Relativity, complex electronic circuits and unproven mathematical equations about primes, yet I can't wrap my head around a goddamn urinal syphon.

[@TheHutchy01]

It's an interesting engineering solution to solve a problem that has never been relevant in any public bathroom I've visited as it appears most punters don't bother actually using the plumbing fixtures, instead preferring the floor near them.

[@andydjbadger]

Even the most dull stuff is made interesting by Big Clive.

[@krnlg]

Or rather, almost everything is interesting if looked at in the right way! :)

[@1Mehdi05]

The main siphon with the large diameter is too large for the trickle of water to start. the second stage with the small diameter is easy to start with the trickle of water. so when the water starts that siphon the inrush of water from the second stage adds the additional water required to start the main siphon stage. The air tube on the side is used to break the siphon by letting air in. If you can connect an air tube to the outside you can adjust how much water will siphon out the tank before allowing air in to break the siphon by adjusting the air inlet height

[@Mr_Blinky]

Multiple bell syphons working in a 'series' manner to make a hydro-timer so the cistern can be filled very fast but it won't finally syphon the water down until one or two of the smaller syphons have filled and emptied many times using the pressure of the water to trickle into the smaller syphons. That's my guess anyway.

[@rchaffer]

The legendary pen is getting low on ink

[@BigClive]

It is. I'll have to refill it.

[@dantasleonardoyou]

Sorry, but I have to disagree! I think it was very interesting and I'm really anxious to see if somebody can help to explain how it works!

[@shugthehornyhaggis]

moved

[@shugthehornyhaggis]

...

[@tylergarza6632]

and it's one thing to thumb it down, its another to fucking reply to his comment and tell him you did so, as if you're at all important. go fuck yourself.

[@nic12344]

This is a modified bell syphon! I will try to explain how it works, but it is a bit complex. (and English is my second language) First, in the sealed base of the apparatus, there is a cup in which the main (larger) pvc pipe is coming down. This creates sort of a p-trap (same as those under sinks) and it traps water in it to act as a valve to prevent air from going down. The main pipe and the bell (dome) are full of air over the waterline of the cup.As the water fills up in the tank, water level will also go up inside the bell . Meanwhile, the air is pushed down the main tube until it reaches the bottom of the main tube. Just before it "burps" air, the pressure of air is higher than the atmospheric pressure. As it continues to go down, it will "burp" air into the cup and air pressure will drop drastically and will create a vacuum inside the main tube. Then, the water in the bell will quickly rise and flush down the main pipe. As bigclivedotcom said, as the water inside the tank is slowly rising and the diameter of the main pipe is large, if you did not have this cup (p-trap), water would only drizzle down the main pipe. But since the p-trap create a sudden vacuum, a large amount of water means that no air can go back up and it will syphon the rest of the water of the tank. Then, as the water level in the tank goes down, the breather pipe (small pipe in the bell) will suck air in and the pressure will equalize (is that the right word?) and the vacuum will be "broken". The water level will then rise again in the tank and the cycle go again. As for the rest of the apparatus now, the small pvc pipe, the copper tube and the miniature bell syphon on top are used for when the syphon as not been used in a while and the water in the cup is evaporated or when it is it's first use and the cup is empty. As there is no vacuum created, water will only drizzle from the cup even if the main tube is full. I don't fully understand how this part works yet, but I'm working on it!

[@fxm5715]

It's nice to see the occasional, "Hmm, I don't know." video. That and showing the mistakes along the way to a successful design, like Mattias Wandel at woodgears and John Mills at doubleboost. Love your channel Clive!

[@NekoSteamBoy]

Its like the Matrjoschka of Piss

[@nunosoares3159]

The first time the system is put to work all vessels will be empty so the air trapped on top of syphon bell have an escape route open trough the big stand pipe and drain line. When water level reaches the top of big stand pipe starts drippling down as, as you said, the filling water has a very slow flow rate to iniciate the syphoning effect. As the water continuous to dripp down will fill up the vessel on bottom of the big stand pipe creating a water seal, from now on the air trapped inside the top of syphon bell has no more escape route (at this time the copper tube tip and the bottom of smallest bell inside the upper vessel are already bellow water level) so the water stop rising inside the syphon bell. From now on, inside the bell, water level will rise only inside the copper pipe and inside the smallest bell syphon (inside the upper vessel) as inside this two the air can escape down trough the drain line. Water level will continue to rise on the tank until it reaches the top of smaller stand pipe inside the smaller syphon, and this will start syphoning lowering the water level inside the top vessel (note that this syphoning effect will be more powerfull than the speed of water filling the vessel from the small hole on bottom of it). As the water level inside the top vessel lowers, the copper pipe tip will be clear above water and the air trapped on top of syphon bell will escape through it allowing the water ingress into the syphon bell and now sufficient to finally iniciate the syphon effect on system and empty the tank. On the next time the tank start to fill up the vessel on bottom of big stand pipe will be already full of water from previous discharge. So the air inside the syphon bell will not escape through it cose the water seal is already there, but will escape through the copper pipe and the small stand pipe (note that upper vessel now empty as it have a drain/fill hole on bottom) until the water level again block it and all above process repeats. Sorry about my english and so many words...

[@sc0tte1-416]

We had one of these 'constantly filling tanks' over the urinals at my elementary school in the late 80s/early 90s...we used to fill it up with toilet paper because we were big jackasses and it would start overflowing. I didn't think they still used this type, rather they went with motion sensors because it seems like a waste of water.

[@AureliusR]

Yup, was in primary school and remember those. There would be a big tank mounted up high on the wall, sometimes with no lid on top, and it would feed a bank of full-height urinals (the ones they got rid of so your piss doesn't splash on your shoes). You could always hear a trickle of water running, and they would all simultaneously flush every few minutes.

[@IDoNotLikeHandlesOnYT]

Now it splashes on your legs instead…

[@sc0tte1-416]

***** Yep those are exactly the ones

[@charmio]

Wonderful! Practical Engineering just acknowledged your brilliance Clive. Prepare for a few more people joining the community!

[@bborkzilla]

It's a bell syphon - if you search for that around here you'll find several animations and even a cut away or two to demonstrate what each part does.

[@BigClive]

I thought it was a standard Bell syphon too, but it's much more complex to allow high dumping with a very slow fill rate.

[@bborkzilla]

It seems some of the extra complexity may be there to prevent the loud gurgling that accompanies the vacuum lock breaking - for instance the little tube that goes from the bottom of the bell up to the air chamber.

[@ronerx]

It's a mystery wrapped in an enigma! It might be a bell valve? I tried, without success to built a bell valve siphon for a hydroponic / aquarium project a while back. I think that airline near the bottom is the siphon break to keep the tank from constantly emptying one the siphon has started.

[@nobodyuknow2490]

it's Syphon-Ception! WE MUST GO DEEPER!

[@davebirkenhead6810]

i think its a cascade system, as the air pressure increases in the dome it pushes the water from the bottom reservoir to the middle res. and up till top syphons, the base to dome pipe stops this happening till the water level in the sistern reaches the level of the top of the blead pipe

[@comettoPL]

Big siphon needs to be filled quickly to start siphoning - otherwise it will only leak at slow rate. So, when the tank is full and little siphon starts siphoning, it floods big siphon and entire device starts flushing.

[@chrisbellis4762]

Dear Clive, I am so pleased that you too are having problems understanding the inner workings. I have one to replace that is contantly running through. It has got me guessing. I notice that another one of your followers has had the same problem. I look forward to your update that explains it all. Keep up the good work Thanking you in anticipation Chris

[@bridgendesar]

I wonder why it has a copper pipe in it, when everything else is plastic?

[@LateNightHacks]

probably: cheaper to make that bent shape out of pipe than PVC -copper is one of the few metals that can stand all the chemicals in urine- engineered single point of failure, copper will eventually corrode

[@locouk]

LateNightHacks Urine won't contact any of this, not unless you climb up and pee into the filler tank.

[@RFC3514]

You realise no urine goes through this, right? It's part of the flushing system, not the sewage system.

[@SuperAWaC]

HEY IF YOU DIDNT REALIZE ALREADY NO URINE COMES IN CONTACT WITH IT

[@anononomous]

@Green Silver That would be an extreme version of top decking someone's toilet.

[@SuburbanStewards]

The extra autosyphon's allow a very small amount of liquid to fill a cistern, and to trigger a dump out of a large diameter pipe without it "stalling" and locking between charge and discharge cycles , The air draw tube from the outside is used to break the seal :-) Look up "Better bell syphon" From Bigelow Brook Farm

[@madhatte73]

Seems to be some sort of hydraulic bistable multivibrator. Holds level between top and bottom setpoints such that it always has sufficient head to flush.

[@BigClive]

You mean like a schitt trigger?

[@beachwebcam]

Never change, Clive!

[@ManosHalikis]

Well, the upper the air inlet mini-system must be the trigger for the vacuum that triggers the main siphonage from the beefier one, that gets helped to stop when the tank empties by that little white one on the cup that sucks air. And then, drip by drip, the system goes back to that critical situation that retriggers the mini-system again. Or something like that!:)

[@madhatte73]

Oh snap, good one!

[@anthonyshiels9273]

When I was in Primary School in the 1960's the Head Master was called Mícheál Mac Oireachtaigh or Michael Geraghty in English. In addition to administering the Cane he also did the maintenance on the water pump and the header cisterns on the urinals in both of the toilets. I remember him adjusting the water tap over the cisterns. If you entered the toilet in an inappropriate manner as he was adjusting the water flow he would grab you and bring you to his classroom in order to dish out "6 of the best". You only ran into the toilets ONCE during your time there. The Cane was a Hazel rod about a yard in length.

[@wilhobbs207]

Hi Bigclive. ..unrelated question. Did you apply to KZbin for your 100,000 sub silver play button?

[@BigClive]

Yes i did. Months ago. No sign of it yet.

[@wilhobbs207]

Congratulations

[@davidnull5590]

Is there anyone your subscribers can contact to encourage the process?

[@epakai]

I bet they can't find how to mail it to the Isle of Man.

[@davidnull5590]

Clive should make it clear to them that he isn't in the United Kingdom. That should confuse them for awhile.

[@Obliterous]

the wee pipe connected to the outside is called a siphon breaker. its there to help break the siphon action when the water level gets low. the copper pipe and small vertical pipe are air escapes that allow air out of the primary siphon without forcing it to go down the main drain.

[@carlyonbay45]

Strange and mysterious things go on in public toilets - it could be a mistake to probe any deeper .

[@buddyclem7328]

It's probably best not to question or investigate any strange noises coming from the men's room.

[@RFC3514]

The exact workings are hard to figure out without measuring things (or seeing it in action through some "windows" cut into the casing), but the various pipes are probably there to ensure a few things: 1. That an air "bubble" doesn't prevent it from filling up properly, 2. That it actually flushes in one go, instead of just trickling, and (possibly - though unlikely in this case, since it's meant to be fully automatic) 3. That it does trickle if the water gets above a certain level but it's not meant to flush yet. The pipe with the mini-syphon is probably the starter. It's hard to tell (because it's broken apart sightly out of frame), but it seems that the copper pipe went directly to the outlet, and not into the off-centre "cup". That suggests that it's either meant as a safety mechanism, as a way to drain the starter at the end of the flush, or as a way to reduce air pressure in some part of the syphon (and prevent a "bubble" for forming). One of my toilets has a similar mechanism, except everything is on levers and moves around in cryptic ways (dual-flush pressure-assisted self-sealing hydro-voodoo).

[@Swans_And_Ducks]

He's taken the piss.

[@DJJAKEY2009]

Lee Hayes "If you like jokes about pissing... then urine for a treat"

[@Alexander_Sannikov]

That looks like super high-tech fluid dynamics passive-action urinal flusher computer.

[@solidamber]

is it a timer? when all the water drains from the tank we will evok article 50

[@WeAreGRID]

The big one fills the bottom cup, but it wont go over a certain level, so it wont go say over half the cup, and then the upper siphon actually fills the cup the rest of the way, so essentially its the top trigger part of it, and the copper pipe is just to empty the cup out or something to that effect, its just balancing, either one siphons and the other empties or vice versa, and essentially it gets over that point, fills the lower cup, and siphons all the water out the tank

[@thepussygrabbingfamilyvalu557]

that's what she said

[@WeAreGRID]

***** the big pipe.

[@Coolkeys2009]

Can you put it back together and make a test rig?

[@alexandramiller9887]

Hi

[@alexandramiller9887]

Hi

[@alexandramiller9887]

Hi

[@alexandramiller9887]

u dont know whats going on xD

[@sebimoe]

It would be great if he put it together, and dremmeled out side of the bottom container, then wrap a PET sheet or stretch wrap foil around it

[@hoopoo3721]

Wow a reliable bell siphon with 4 bell siphons in one! they even fixed the vapor locking, refilling and flow problems.

[@zanpekosak2383]

Who camr because of Practical Engineering?

[@poiuytrewq4645]

AirsoftSlo came here you mean?

[@chrono_magucus515]

Me

[@TheOldGuyPhil]

Me too, and it is refreshing to see you stumped Clive.... Like most, I love your videos!!!

[@jmtruthful3273]

Me

[@Davidorino]

Me

[@rich3500]

Crikey that sure is complicated. But what really stands out is the large translucent cover that it all fits in. I think it would make a fantastic lamp if it was stuffed with LEDs. Go on Clive, you know you can do it!

[@davidnull5590]

I must be leading a very quiet and sheltered life: I've never had the urge to search E-Bay in the middle of the night in hopes of scoring a new 'urinal auto-siphon' from China. I hope there a special program for my condition.

[@jazwiec9379]

Just saw this video today. And I think I know the answer to your question, why there are so many syphons-in-syphons. Actually, you pointed the essence of the problem at the very beging of the video: the incomming water fills the tank very slowly. Now, the vacuum-based syphon action won't happen unless the output pipe is fully closed with running water - otherwise the syphon would just leak the amount equal to the water comming through filling pipe. That's why there is a tiny syphon with throughput much smaller than the filling water, so that in this one the vacuum action will certainly happen. Once it happens, the amount of water that goes through it will trigger another such action in a larger syphon and so on, so on, until the largest syphon empties the entire tank. That's how it works.

[@BrendanPerkins]

More fun than watching fireworks. :)

[@tyvole2387]

Mostly because all the good stuff has been banned due to idiots misusing them. They don't have to be boring, it's just that the boring shit's all we're allowed to play with now. I think it's a crying shame.

[@davidhaney1394]

clive , you have an uncanny knack of making everything interesting ...

[@BartJBols]

After billion hours of google i found this patent describing a multi syphon trigger mechanism for siphons used to ensure starting conditions are always equal no matter what input or output happens www.google.tl/patents/US4319601

[@kirankankipati-thelinuxcha689]

I think the small syphon is meant for regular water flush with small quantities just to keep the urinal wet and odour free. The big syphon is meant for bulk flush to clean the urinal with a huge burst of water and wash away the urinal. The size of these cups determines the duration and water quantity which is carefully engineered. Its an engineering wonder :) Its just my guess. I often thought these are solenoid and electronically programmed. But after seeing this video I can see an excellent fool-proof flush mechanism which can work 24/7 without any electronic control circuits. Nice video. Thanks for random stuff.

[@jakp8777]

Whys the pipe copper and not a cheaper material?

[@SonyFoLife]

My guess is because it happened to be cheaper for that factory to buy and use copper tube than to try and make the tube out of plastic or something else. Not that copper is a better material for the task per se but that it was better for the factory. I don't really know either way but that's my guess

[@jakp8777]

Da S why not just aluminum then? Cheaper the copper and still metal.

[@mbaker335]

Copper is antimicrobial. Algae will not grow on it and block the pipe. aluminium would block up quite quickly with a slimy goo. This property of copper is why older door handles and door plates were always made of copper or brass. Slowed the transfer of disease between people using door handles.

[@petermcarthur7450]

Try forming that shape out of PVC or aluminium and see how far you get. ;-)

[@PWingert1966]

I suspect that the diameter of the copper pipe is important. If it gets clogged there is not enough back pressure to clear the clog and so you don't want to have a bacterial soup floating at the top of the pipe where he curve is preventing flow due to vacuum pressure is a key to this copper pipe working like a valve and like a p-trap at different times in the cycle. Cascading triggering makes sense with the aim of having enough potential energy stored at each stage to allow the cycle to trigger as each stage. Potential energy has to be part of the equation and overcoming vacuum pressure has to be another part and don't forget about gravity. The other key to understanding this is to think of how you siphon gas from a tank. You first apply a positive pressure to the hose (by blowing aka increasing air pressure) to provide a well of energy and build the potential energy needed to pull the gasoline and overcoming inertia and thus pulling the liquid out of the tank then: when you release that energy it creates a vacuum that does the pulling and overcomes both friction and inertia of the gasoline. Its much harder to get the same effect by just providing a vacuum (Sucking n the end of the hose...gravity and back pressure actually pulls the liquid back into the tank). If you leave it to continue you can actually drain the tank I know that I have most of the pieces in place but not sure exactly how they apply in the siphon. It is a "siphon-pump" after all that is working almost exactly like siphoning gas from a tank.

[@vacexpert2020]

Last I checked older schools in the U.S use a similar system, though the fill valve is controlled by a motion controller that also controls the lights

[@animefreak5757]

i'm pretty sure those vent holes are air inlets. Otherwise it'd create a vacuum inside the entire case wouldn't it?

[@AureliusR]

But that's what you _want_. You _want_ a vacuum to suck more water in from the big tank this sits in.

[@GodlikeIridium]

Never seen such a system. Here we went from normal valves to IR sensors directly. But this is a really interesting siphon!

[@KarlBunker]

It looks like some urinal-siphon design engineer was getting paid by the hour.

[@pyr666]

it's using the air inside as a compressible working fluid. the water rises until it covers the entrance of that vent pipe on the outer casing, at which point the air inside starts to compress. the top-most assembly serves to equalize the pressure between the top of the outer shell and the cavity at the bottom of the assembly. that setup ensures the siphon won't start until the water level outside the device is well above the entire thing. in normal operation, the air would eventually be compressed enough to force itself out and start the siphon. if that fails, the water continues to rise and the pressure equalizing pipe serves as a secondary bell siphon, with the copper pipe server as the secondary equalizer.

[@RandomHacks]

Is this a mindfuck to everyone else or should I watch this when sober?

[@lorenzo52877]

I really enjoy your videos. saves me the trouble of riuning things around the house to see how they work

[@happy543210]

can you provide a patent number?

[@katelibby713]

happy543210 good idea

[@rusty0101]

Ok, the first syphon (large diameter) does as you say, let's the cup fill a small amount but without enough water to actually trigger the flush syphon. The copper tube provides a primary trigger that when the syphon in that one takes over it fills the cup with water which when it overflows causes the large diameter tube to act as a primary syphon as you would expect. What keeps that from happening is that the copper tube acts as a syphon with one end in water (in the cup) but not enough to trigger it's syphoning from the cup. The cup needs a specific amount of water for that to happen, so the third set of tubes and the syphon cup there hold back some water in the cup after the main syphon kicks in, with enough force to pull water back through the copper pipe as well. The reason that the vent hole is in the top of that cup is so that once fhe flush is done, the water that's in that part of the cup can settle back into the cup the end of the copper pipe is in.The reason for the tube off to the side to the wall of the main syphon cup (the upside down dome, large) is there because if it were not there, air in that cup would prevent the syphon from filling in the first place (once the first syphon floods and it becomes a pressure vessel rather than just an upside down cup over the system.An alterntive for this would be a one way valve actuallly in the top or end of that cup, that allows water to enter the cup as the water level rises, then closes once the syphon action starts. I suspect that they get better efficiency with the valveat the bottom though.

[@wb6wsn]

Reminds me of an old Triumph carburetor; multiple gegaws creating a contraption simply begging to be replaced by an injector nozzle.

[@jasong2004]

Big Clive... You make the most mundane things absolutely fascinating. Thank you for your channel. I never comment but it's just incredible how much you've filled my mind with new wonder at the world.

[@BartJBols]

Why are your hands ALWAYS mangled in different ways??? what kind of kinky stuff do you do that you constantly have wounds on your hands?

[@BigClive]

Work and taking stuff to bits.

[@BartJBols]

bigclivedotcom poor you, maybe wear gloves?

[@Dragonkin121]

he said he needs to take stuff to bits, but if you do wear gloves it could potentially be more dangerous as you dont get the actual hand feel you need for taking things apart

[@jubjuber1]

I think if I understand correctly, the copper pipe and siphon stack create pressure in the bottom chamber as water fills over them, this counteracts weight of the water inside the closed chamber, so it won't overflow the cup. When water reaches over the top hole, it floods through releasing all the air pressure inside and allows the main funnel to drain the chamber, but makes sure it's all the way full before it happens

[@budude2]

The "Inception" urinal valve...

[@phainesthai]

The small tube on the dome cover is to let air in when the water level has gone down, its to break the syphon, it will let air into the top, its also a way to keep it quiet.

[@ionizedodds1601]

My Brian :'(

[@Josh_2976]

Ionized Odds Brian isn't yours or anyone else's he's a person.

[@johnandshelly82]

Ionized Odds he's a very naughty boy.

[@LordClunk]

I think the plastic hose is there to break the siphon in a way to leave it primed. And the copper pipe is to prime it for first use. With so many chambers, they would all need to be bled for first use. We make similar things at work, and I am pretty sure the plastic dome comes off for installing and for priming. But don't hold me to that.

[@rimmersbryggeri]

Looks like a perpetual motion machine.

[@johnrobinson357]

Fluid dynamics a very fascination form of engineering. this is with no doubt one of your better " take to bits " videos . Yeah' i am trying to figure flow and function. With not a lot of answers. it is fairly simple - in it's concept and sort of it's function. Good stuff clive - again. Make my brain twist.....but i like that.

[@pspkiller91]

"I don't have urinals in my house, as such..." I think Clive pisses in the sink.

[@BigClive]

In a way a toilet is like a urinal, but multi-purpose.

[@stevesbuttdocter1173]

mur38 you're taking the piss 😂

[@porouscrump]

I have experience building various auto siphons and this one is indeed a head scratcher. The air pipe at the bottom on the outside is to let air INTO the siphon chamber and break the siphon. My guess on the rest of it is that it's a three stage siphon. There is the main one with the basic components, a redundant one to make sure everything starts up properly, and one that flows continuously. Since the water and urine are coming into the system constantly, some level of siphoning is also always happening. If there's a massive influx of fluid suddenly, then it can drain the whole thing down to that air inlet.

[@SubjektDelta]

Somehow I have a strange urge to pee right now..

[@RWL2012]

Calvin K me too :3

[@RWL2012]

EmptyMagazine LOL!!!

[@quantumleap359]

Golden Showers for everyone below!

[@10010Linus]

LEMON PARTY!!!

[@reinux]

The air pipe at the bottom is to pull air in when the water level gets low. That way you can be assured that the siphon will be broken. Otherwise, sometimes the siphon will continue draining forever with the water level low. The multiple layers of siphoning is to ensure that it'll drain regardless of how fast or slow the incoming water is. Autosiphons can be extremely finicky.

[@arthurschroeder3003]

Here in U.S. it would be ripped off the wall from vandals right away.

[@rak3shpai]

This is indeed surprisingly complex. If the goal is to let a container fill up to a point, and then drain it to a point, it can be achieved with a simple bell syphon. The construction of a bell syphon is simply two concentric tubes with strategically placed holes - you should find tons of videos on building one. Bell syphons have been used in aquaponics for a long time, which is where I heard of them. They are simple mechanical devices, easy to DIY with PVC pipes, require no electrical power, and have no moving parts which makes it very reliable. I've built a bell syphon for a little project, and it has worked flawlessly for years. This complicated arrangement of tubes and cups seems unnecessarily complex. Can't imagine what this complexity adds, when a simple bell syphon does the job so well.

[@jimmartin7899]

Its a redundant system so if one siphon gets clogged up the other siphon builds suction to suck the clog through. Urine contains salts and minerals that build up this redundant siphon is designed to over come this aspect of processing urine through it.

[@CertifiedGhoul]

This was a really fun video to watch. I love your electrical videos but sometimes it is just fun to watch you tear apart appliances.

[@Alexor715]

"I thought it's gonna be simple." "Not sure how to use this." "Oh that's complicated." "When one of these pipes... wait, why there are two?" - the most engineer-ish statements ever 🤣

[@Slikx666]

I think the simplest way of explaining how it works is Magic!

[@logtec1977]

The large diam pipe is an overflow tube, to prevent the tank from overflowing if the siphon failed. Kinda like in a toilet tank, if the fill valve fails to stop the incoming water, the water just goes down the overflow tube into the toilet bowl, instead of spilling out of the top of the tank onto the floor and flooding your house.

[@woowooNeedsFaith]

I suspect that the key to understanding this is to think about the water levels of different compartments before the syphoning starts. I guess that the water level is used to function as an air valve. For example, the water can't flow into an upside down cup if the air in it can't escape. It would probably be helpful to draw (exact) relative levels of each opening of cups and pipes.

[@richlaue]

I think that thin pipe is only for help in breaking the siphon. If you note the height of the entry, it allows extra air in when water level. This pipe is common in flood and drain hydrponics

[@samheasmanwhite]

The lower cup allows air pressure to build inside the main dome so that the water level outside can get higher than the main pipe. The copper pipe looks like the final exit to be closed to allow the pressure to build up and the small plastic pipe seems to be the one that lets the air out of the top once the pressure is high enough to push air through it's little cup, letting the water quickly rise above the main tube and start the siphoning. Not quite sure but that's what it looks like.

[@RambozoClown]

A crazy combination of simple and complex, with the only moving part being the water. With the cost of copper, I wonder why that was used instead of plastic or even aluminum. So a mixture of cheap and expensive, too. A clear one would be interesting to watch in action.

[@chevsev]

the small tube in the outer housing is to break the syphon, as the water level rises it reaches the big tube first flows down and fills the cup allowing a trickle of water to flow but air can still make it up the copper pipe until the second syphon fills and flushes filling the lower cavity blocking air flow setting off the big syphon to flush. This way they can have a trickle of water delaying the flush and could be argued for freshness all with no moving parts.

[@beefcakeandgravy]

The little tube sticking out of the side can't be an air relief as it will be underwater. I THINK the whole unit is filled from that little external pipe ONLY and then when it is full, it all empties from the top syphon when that overflows into the main unit, then drags the rest of the water out with it from underneath the dome. The dome will keep all the water OUT of the syphons until the little one fills, overflows, overflows again and then dumps everything out the bottom making the dome the largest of the syphons. So, little syphon overflows into no.2, which overflows into no.3, which then overflows into no.4 (the 1" pipe) making the last step to draw all the water up inside the dome, and out of the main pipe. I count 4 syphons total.

[@Spinner5151]

Not sure if anyone answered this correctly but there always has to be a 'water trap' between the 'dirty water' and the clean water supply. It's in "The Regs"... In the same way there is an S or P bend behind your bog / water closet or "Jacks" or a water trap under a sink. Otherwise the smell of the sewarage / drains / sluury tank /cess pit would permiate the bathroom / kitchen or pissior. That is the bottom chamber. The rest is pressure release and a device to make sure the bottom trap is always refilled after every flush. Now please wash your hands. You're welcome. :-)