Hello, it’s Jonathan from Melbourne Aquaponics.
Today, we're going to talk about the bell siphon.
The function of the bell siphon is to allow the water level into the growbed to go up
and down.
The reason why you want the water level into your growbed to vary up and down several times
per day is to bring some oxygen to the roots of your vegetables.
Otherwise, they will rot.
But also, to bring some oxygen to your bacteria.
You know that the bacteria is basically the biological filter of the growbed.
Right?
They live - of the aquaponics setup.
They live on the media that is into the growbed and they need a lot of oxygen to live.
Right?
They are aerobic and if you don't have a system that is going to allow your water level to
go up and down, the problem is that you’re going to have some deficiencies in oxygen.
So in aquaponics, we work with the fish pooh.
Right?
So you got a lot of organic matters into the growbed and those organic matters are going
to be transformed by the bacteria.
But those organic matters if there is no flush onto the system, they’re going to be accumulated
between the media and they're going to clog very easily.
So if you design a system without a bell siphon or any other system to allow the water level
to vary, if you are in a constant-level growbed, after a few months, you're going to have some
parts of the growbed that are going to turn anaerobic And that’s when you’re going
to start to smell it.
It's going to smell very bad.
You're going to start to have some fermentation, and obviously, you're not going to have the
transformation of the ammonia in nitrite and and the nitrite in nitrate, which means that
basically, you're going to have a pick of pollution into your water and obviously, your
fish are going to die or they're going to stress very much.
That's why a bell siphon is so important .It allows the water to go up and down.
Each time the water goes down, the bacteria have direct access to the oxygen from the
atmosphere.
When the water level is up, the little bubbles of air are trapped between the media and inside
the media as well because most of the time we choose a porous media in aquaponics.
So you got a lot of oxygen everywhere all the time.
Even when the water is high, you still have a lot of oxygen.
And then obviously, the water is going to drop very soon because the bell siphon is
going to flush.
And the bacteria are going to have access to the oxygen from the atmosphere again.
So that's really the role of the bell siphon, it's to really keep the environment aerobic,
100% aerobic.
And that's a key in aquaponics.
Now, you can reach this kind of -- the same result with different other systems.
You know, you can use a timer on a pump with a little hole on the evacuation pipe of the
siphon, all these kinds of things, but I think the bell siphon is really the most efficient
way to work.
And obviously it's powered by gravity so it doesn't consume any electricity.
It allows you to work with quite small pumps because you don't need to have such a big
volume of water to renew the whole system having a constant level growbed.
Here, you know, the bell siphon, you can only renew the total volume of the growbed twice
per hour, and it's going to be completely fine.
So really, I think that's really the key of aquaponics the bell siphon.
So now, let's have a look of what a bell siphon is composed of.
So first you can see that we got this external pipe here.
It's -- I used a bit more than 100 -- some 100 mm. pipes.
Sometimes I use 120.
So basically, this one, the external one has no real -- it's not very important, but you
won’t to be able to put your hand inside.
Right?
Because if you've got some media that falls inside or anything, you want to be able to
clean inside.
So the function of this first pipe is to keep the media away from the inside of the siphon.
Right?
You could use another material.
I use a pipe with some holes inside so it allows the water to go, but it keeps the media
away from the inside of the siphon.
I also use a cap that I put on top.
So in this case, I know that everything inside is completely protected, and I'm not going
to have too much dust or media or whatever inside.
Then inside you got a bell so that's why it's called a bell siphon.
You can see that on the bell you got this kind of little air pipe and here you got also
a stand-up pipe.
So what we want to understand here if you want a technical explanation of how the siphon
works, obviously, the stand-up pipe is plugged here straight.
It's connected to this pipe here.
And without the bell, you would have a constant flow.
The constant flow would be – the constant level will be determined by the top of this
pipe.
Right?
So basically, the level in your growbed is going to increase, increase, increase because
the pump is turned on.
Once it reaches this level, the water starts to fall inside the pipe and it returns to
the fish tank.
So basically, you can control the top level of the growbed by the length of this pipe
here.
If you want the water level to be a bit lower, you can get it a bit lower.
But that's basically what you got when you got a constant flow.
But here we work with a bell siphon.
So the bell is coming on top of this pipe here, and it's going to determine the minimum
level of water into the growbed.
Right?
So what happens is that the water is coming from those little holes on the bottom of the
pipe.
Right?
It's going to raise inside and it's going to fall into the black pipe.
Right?
the water flows here on a constant flow level.
On a constant level growbed, the water is going to fall into this black pipe, and the
water flow going out of this black pipe is going to be equal to the water flow coming
from the pump.
Right?
So basically the water coming from the pump goes into the growbed and the same quantity
is going back into the fish tank.
Now, when you put a bell on top of this, it changes the behavior of the system.
So what is happening here now is that the water is falling into this black pipe.
Okay?
And it's coming inside the bell.
It's falling into the black pipe.
What happens is that in this black pipe, the pipe is quite high.
Right?
And you got the water is falling.
It’s a waterfall inside.
And when the water falls, it accelerates.
So the speed of the water is going to increase very much.
Now, what happens is that you need to understand that in Physics, there is a constant.
The constant is that the pressure multiplied by the speed of the water is always constant,
for a certain water flow.
Right?
So here, when your water falls into this pipe, it’s going to accelerate, but because the
speed of the water is going to increase, the pressure is going to decrease.
And so when you got your bell on top, obviously, you got a bit of emptiness here and you got
this water that is falling into the black pipe.
So because the pressure is going to decrease, here you got it -- you're going to have a
de-pressure and on this part, all the air is going to be sucked in the fish tank.
Therefore, here it’s going to be full of water, as well.
So basically, the water flow here is going to increase then.
It's going to increase.
It’s going to become -- the section of the pipe is going to be full of water at high
speed, and therefore, the water flow going out of the bell siphon is going to be higher
than the water flow coming from the pump.
By doing so, you understand that the water level is going decrease into your growbed.
The water level decreases, decreases, decreases, decreases until it reaches the bottom of the
bell.
So at the bottom of the bell, we got this little air pipe.
It’s going to allow the pressure inside as a part -- inside the bell to be balanced
with the atmosphere.
In this case, the bell siphon is going to stop.
So that's exactly how it's going to work.
Right?
The water level is going to raise because you’re going to pump that is pumping some
water into the growbed.
Once it's reached the top of the black pipe inside the bell, the bell siphon is going
to start because it's going to create a de-pressure.
The pressure is going to be very low inside.
It's going to suck the air and then it's going to be full of water.
So all the water flow is going to increase dramatically and therefore, the level of the
growbed, the level of the water into the growbed is going to decrease.
And it's going to stop, and again, it's going to increase, increasing, increase, decrease.
So it’s going to be – you want to dimension it -- well, actually, the water-pump is going
to determine the frequency of those flush.
You want a water pump that is twice the size of your growbed.
So let's say you got a growbed of 500 liters.
You want a water pump that is 1000 liters per hour because you want to be able to flush
approximately twice the size of your growbed per hour.
And yeah, that's how it works.
I think it's quite straightforward.
Now, if you want it to work efficiently, you need to find the exact width dimensions of
pipes and the good length and the good diameter for all the components of the bell siphon.
If you don't have the exact same dimensions like a few millimeters, the bell siphon is
not going to work.
The bell siphon, each bell siphon is adapted to a specific size of pump.
And that’s very important to understand that.
If you buy a bell siphon that you run up to 4000 liters per hour of pump and you plug
it to a 5000 liters per hour of pump, the bell siphon is never going to stop.
So the water level is always going to stay down.
So it's not going to work.
If you want to design your own bell siphon, you can play with different pipes, different
dimensions.
It's always a bit tricky to find the exact dimensions.
Now, if you want to create your own bell siphon for a backyard aquaponics system, so from
200 liters growbed to maybe 800 liters growbed, you can use our video because we got one video.
You can purchase the video.
You’ve got a step by step process to build your own bell siphon adapted to the dimensions
I just told you.
So it's to go with the pump that is going from 750-2500 liters per hour and there, in
this video, I'll give you the exact dimensions for these specific dimensions of pump.
Yeah, now, again if you want to build your own for other dimensions, you're going to
be able to do it definitely, but it's going to take a few hours and a few trials and mistakes
before you are able to find a good setting.
I hope you enjoyed the video.
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Please give me your like if you liked the video, if it's useful for you.
In the comments, please tell me what kind of video would help you if you are stuck somewhere
in aquaponics.
Please let me know what would be interesting for you to know and to understand in aquaponics.
You can also download our free bonus video which is talking about how to keep your vegetables
green, strong, and healthy in aquaponics.
And yeah, I will see you in the next video.
Thanks for watching.
Cheers!