(upbeat music) - If you remove the tray
from your washing machine, you'll find a really interesting
hydrodynamic mechanism. Specifically, in the fabric
softener tray, this bit here. That's a lid, here's
the compartment itself, and you'll notice it's completely sealed. If I fill this thing with liquid, there's nowhere for it to go. But if I keep filling,
eventually it reaches the opening at the top of this tube here, and it starts to pour through that opening and it comes out the back here. But the liquid doesn't empty completely, it remains at the same
level as that opening at the top of the tube. So how is it that when
I put fabric softener in the washing machine and I come back after the wash is finished, that compartment is completely empty? How does the liquid get out? Well, here's a clue. When I put this lid back
on watch what happens. (water dribbling) The liquid empties out. Well, how is that? Let's take a closer look at the lid. There's nothing particularly
interesting about the lid. You've got this tube here, there's nothing interesting
at the bottom of it, and that fits over the tube that's embedded in the tray itself. Let's see what happens when
we slowly fill the tray with liquid when the lid is on. The tray fills up and
fills up and fills up, until you get to a certain point and then it all drains away. The mechanism is called
a Pythagorean siphon, or Pythagorean cup, or
a greedy cup siphon. I've seen two-dimensional
animations of it online, but I thought even better, would be to build a
two-dimensional version of the Pythagorean cup. This is obviously not a
two-dimensional object, it's three-dimensional, because we live in a
three-dimensional universe. But it is two-dimensional in some sense. In the sense that nothing
interesting is happening in that third dimension, only this dimension and this dimension. Let's see what happens
when we start pouring a liquid into it. The level of liquid in these two chambers is the same as the level of
liquid in the main chambers. That's because the pressure is the same in both of those places. But when the liquid
reaches the top edge here, and spills into that central chamber, it falls down because of gravity. But crucially, the liquid
forms a kind of seal because of surface tension. Like if air was able to
break up through the liquid, then the siphon affect
wouldn't work at all. But because of the seal created by the surface tension of the liquid, the weight of all that
water in the central chamber pulls the rest of the
liquid out of the device until it's almost completely empty. And of course, that's the
purpose of the mechanism in the fabric softener tray. You put your fabric softener in there and you're told, "Don't
put it above this line," otherwise, it's all gonna go. And then when the machine
wants the fabric softener, it adds water to the tray until it reaches that critical level. Then it all pours out
fabric softener and all. It's actually quite similar
to a regular siphon. The big difference is it's self-starting. Like with a regular siphon, you need to suck on the
pipe to bring the fluid up to the top and back down again, below the level of the top of
the liquid for it to start. But with a greedy cup siphon
that happens automatically, as you're pouring the
liquid into the container. Because the equivalent of
the straw in this example, is below the top of the container. This is the traditional
Pythagorean cup or greedy cup. You just about see the
hole in the bottom there. And here it is in action. (water dripping) Even better, here's a glass version so you can see what's going on inside. There's the hole at the bottom there. And look at the top, you can see the equivalent
of what I've got in my two-dimensional version. At this point in the video, many of you will have
already said out loud, "That's how a toilet works." (sighing) Well, the flush mechanism in a toilet, I wouldn't exactly call
it a greedy cup siphon. It is a siphon though. And actually the way it's
activated is really interesting. Urinals or urinals, depending
on how you pronounce it. Urinals, those ones that flush
repeatedly every few minutes, that's a greedy cup siphon. So the cistern is constantly, slowly being filled with water. It goes up and up and up and up and up, until it reaches the top
of the greedy cup siphon, it all pours out in one flush and then it starts to fill
again and that cycle continues. Not all urinals work in that way, but there are definitely some out there. You know what? Let's, toilets are interesting. It's not a greedy cup siphon. It's not quite the topic of this video. But let's do the toilet. Before we get to the siphon part, here's a really cool mechanism. You've got this float
that controls the flow of water into the cistern. You see, as the water level
rises, the float rises as well. The float is connected to this lever and when it gets to a certain level, it presses on this ballcock
that cuts off the flow of water. So the level of water never
rises above the desired level. But what we're really
interested in for this video, is the siphon mechanism. I've got one of those mechanisms here. I'm gonna take it apart so you can see how it works on the inside. So this pipe here is screwed
into the bottom of the cistern, and that leads to the toilet bowl. So when you flush the toilet, all the water's gonna pass
through here and into the bowl. Let's see what's going on inside. Here we are. And so, when the cistern is full of water, it's full to about here, right? It's not at the top of the siphon yet. And to initiate the siphon
or to prime the siphon, to use the proper terminology, you need to get the
water up over this level. How do you do that? Well, you've got the handle of the toilet that's connected to an arm
which pulls on this thing here and lifts that up. So this is like a piston, almost. So that pulls a whole
lot of water up and over. And by the way, this is, the
bottom is open to the cistern. There's a gap here. So the water from all around
can flow through and in here. So when you pull up like that, you're pulling water from the cistern, up through here and it
initiates the siphon. It primes the siphon that
pulls all the water through. This is actually a one-way valve. So when the water's being
pulled up through here, these two bits flap up
and they allow the water to come up and over until
the whole cistern is empty. There's something really neat about using this mechanism in a toilet, which is if the supply of water into the cistern is a bit leaky, like if it never shuts off, even when the water has reached the desired level in the cistern. Well, in that case, the
flow of water is quite low. It's just gonna dribble over
the top of the siphon there. It's not gonna initiate the siphon, it's just gonna dribble over the top. I can demonstrate that with
my 2D version here actually. Look, if I gently pour
liquid into the siphon, it doesn't actually
start the siphon process, it just dribbles down
that central channel. And that's what happens if
you've got a leaky toilet. If you can hear your toilet just kind of dribbling all the time, you'll notice it's coming into the basin and that's because it's going
over the top of your siphon. One final, really cool
thing about this mechanism, you can choose whether to
completely drain the cistern, when you flush the toilet or
only half drain the cistern. And it's controlled by this piston here. Look, when you pull the
lever on the toilet, it lifts this up. Can you see at the bottom
there's these slats? So what happens is if you keep the lever of the toilet pressed down, this thing stays up in this position. And then as the water
drains out of the cistern, it gets down to this point here, and air can get in through those gaps. And that air cuts off the siphon, so only half the cistern drains. But if you pull the lever and then immediately drop
the lever back down again, this rubber ring here
blocks off the entrance so air can't get in. The siphon remains running until the whole cistern is empty. Not all toilets have this option. And in fact, not all toilets
use a siphon mechanism. It just so happens that all the mechanisms I've ever come across in my
life are the siphon mechanism. Though, I think it might be different in different countries. So do let me know in the comments. That is an unusual request
for comments, isn't it? Hey, don't forget to comment. Specifically, about your toilets. Do though, do tell me about your toilet. Thank you to my Patreon
supporter, Wayne Uroda, for the tip-off on this one. I appreciate you and all
my Patreon supporters. (water pouring) (water dribbling) In the past, if I wanted
to learn something new, then I just kind of
muck through on my own, try and figure things out by myself, Google stuff, read articles. But these days, I've really
come round to the idea that you should invest, if you can, some quality learning time at the very beginning with experts, and it hugely improves the
learning process after that. I'm talking about online video learning. And specifically, about the sponsor of this video, Skillshare. Their courses are usually
around an hour long. And if you invest that
quality learning time at the very beginning, then it vastly accelerates your learning, as you then go on and practice
and learn by yourself. I thought I'd mentioned
some of the courses that I know are good from
a few different areas. Lightroom, a total beginner walkthrough. You might think that Photoshop is the defacto photo editing software. But actually if you wanna take a picture and just improve that picture, then Lightroom is the thing to use. Responsive Web Design, maybe you wanna get
into building websites. If you do, then you need to
know how to make a website that works on mobile and
desktop at the same time. The JavaScript Toolkit, JavaScript
is my language of choice when I'm coding something, 'cause it's the only language I know. And you know, it's a classic example of me learning something
on my own and producing some really smelly code. But now, because I've taken some courses, the JavaScript that I write is, well, it's much better for a start. It's easier to debug. It's more enjoyable. And because I've got this foundation now, when I am coding on my own,
my learning is accelerated. You can try all their courses
for free using my link. If you go to skl.sh/stevemould09201, the link's also in description, the first 500 people to use that link will get two months absolutely free. So you can try all those
courses, no strings attached. So check out Skillshare today. (upbeat music) I hope you enjoyed this video. If you did, don't forget to hit subscribe, and I'll see you next time. (upbeat music continues)
My washing machine is broke and doesn't do shit.
He made a cup that utilizes a bell siphon, the siphon isn't named after him.
Looks like someone went down the rabbit hole from that Indian(?) siphoning GIF from yesterday!