What is a Bell Siphon

In the wonderful world of Aquaponics, simple mechanical and biological theories are put to the test to create a product from a process of nature. The most important control in Hydroponics or Aquaponics systems for the process to function is called a Bell Siphon. What is a Bell Siphon?

A Bell Siphon improves the oxygenation to the roots of the hydronic plants. As the bell siphon drains out the water, the full lengths of the roots are exposed to air regularly keeping the system aerobic. This promotes oxygen intake, aiding in plant growth, & the overall health of the plants.

Using no powers or timers a Bell Siphon controls a necessary function critical for the Hydroponic and Aquaponic systems. A  simple function that is genius and effective.


What is a Bell Siphon


A Bell Siphon is an easy way to drain grow beds in Aquaponics or Hydroponics systems. It can regulate the flow without the need for human or mechanical intervention. The fundamental principles of a Bell Siphon are based on hydrostatics or the relationship between the height of a water column and its pressure. At the highest point in a siphon, the pressure is actually lower than atmospheric pressure, also known as a vacuum in the aquaponics system.

This allows the atmospheric pressure to push water up over the peak of the siphon so gravity can carry it the rest of the way. For most situations, that’s enough theory to describe your typical siphon. It’s a very convenient way to drain a reservoir or transfer a liquid without a pump, electric power, or timers. The Bell Syphon is used in different applications but for this article, we show how important it is in the field of Hydroponics and Aquaponics.

A Bell Syphon has three parts:

  • Reservoir
  • Bell
  • Riser

How Does a Bell Siphon Pipe Work in an Aquaponic System


    • The drained grow bed is first filled with water using a water pump.
    • When the water level reaches the top of the standpipe situated inside the siphon pipe, water will start flowing through the reducer placed at the top of the standpipe and out through the standpipe into the fish tank at low pressure.
    • As the water slowly drains out of the standpipe, water builds up inside the bell and pushes air out through the standpipe. As a result, the pressure inside the bell eventually falls.


    • The resulting low pressure in the bell leads to a pressure difference between the bell and the atmosphere which forces the siphon to fire. Thus, the siphon rapidly pushes out and dumps the water through the standpipe at a much higher pressure until the water level reaches the base of the grow bed.
    • As the water level approaches the base of the siphon pipe, air enters the bell through the slits at the bottom of the siphon pipe which relieves the pressure difference between the bell and the atmosphere, causing the siphon to break and halt the drain of water.


A Bell Siphon is a simple device used in Hydroponics that regulates the flow of water in aquaponic and hydroponic systems easily and efficiently, with no need for human intervention.

The siphon first allows the grow bed to flood, then it automatically drains out the water when it reaches a certain level so as not to flood the system. The siphon also maintains a minimum water level as the excess water is drained automatically.

In Hydroponics and Aquaponics flooding and draining the grow beds is a constant operation that keeps the plants in the system healthy during the growth cycle. It keeps them in contact with the right amount of nutrients and water.

It will also provide oxidization which is also important in plant development. It will slowly fill the tanks and provide plenty of time for the plant’s roots have plenty of time to uptake a good amount of nutrients and water.

When it drains it will do so rapidly that it provides a large amount of air that is used up by bacteria in the bed and at the roots for the plants to grow. This keeps the plants and the system aerobic and healthy. Air is important in the system where bacteria use it for breaking down and processing the fish waste turning it into nutrients that the plant used for food. Without the oxygen in the growth bed that acts as a filter and can’t operate properly. Soon the system would turn anaerobic and fail.

In an Anaerobic state, bacteria break down organic material, and fish waste, without oxygen.  This process gives off methane and hydrogen sulfide, which produces the rotten egg smell of anaerobic digestion.

In its basic function, the bell siphon regulates the health of the bacteria, foremost, and plants in the media bed.  This, in turn, regulates the health of the entire system, plants, bacteria, and fish keeping a fine-tuned ecosystem working in tangent with each other naturally.



Does Singing or Talking to Plants help them grow?

Science has proven that plants:

  • Detect vibration
  • Emit sound waves at levels of 10-240Hz
  • Emit ultrasonic acoustics within 20-300Hz
  • Grow into the direction of vibration
  • That plants make sounds
  • Respond to touch, light, scent, wind & gravity
  • But talking & singing to help them grow is inconclusive ………………………………………………………………….. Read more


Aquaponics System Water Diagram


The Aquaponic System is a recirculating system, water is continuously running through the system.  There are four tanks, a Fishtank, a Float Bed, a Sump tank, and a Media bed.  Water is pumped from the sump tank into the float bed and then drains to the fish tank. The fish tank drains into the media bed and the bell siphon drains the water to the sump tank.


  • As the water fills the Grow Bed
  • the Standpipe limits the maximum fill height of the water.
  • When the water rises it pushed air out of the bell housing pipe and down the Standpipe.
  • Once the water level reaches the top of the Standpipe it begins to drain down the pipe.  This is the beginning stage of the siphon.



How do you Propagate Plants from Cuttings in water?

  • Snip cuttings from the plant.
  • Cut 1/4″ below the node at a 45° angle with a clean knife or scissors.
  • Stick cutting in a clean glass
  • Pour tepid room H2O to cover nodes
  • Change H2O every 3-5 days
  • Wait till the roots grow(this can take weeks to months, depending on the plant)
  • Once roots are 2-5″ Pot in soil ………………………………………………………………………………………. Read more
    • Why You Should Use a Bell Siphon for Water in Aquaponics


    The Bell Siphon does have its limits even though they are far apart.  If the water comes into the media bed too fast or too slow the siphon will not be engaged.  You need to set the Siphon in place and take it through a few operating times. Make some adjustments to the bell to iron out the pump water levels to the grow bed keeping just the right amount of water and oxygen for plant growth.

    The Bell Siphon is not only an integral part of Aquaponics but a fascinating feat of science.  With the ability to flood and drain a tank in a system with one pump greatly lowers the risks of failure.  The siphon runs automatically and consistently giving the plants a stable growing environment. By having even flood drain cycles the plants receive even amounts of air, water, and nutrients in the grow bed.

Adjusting Siphon Bell Pipe in an Aquaponics System

The Bell Siphon in aquaponic systems grow bed does have its limits, even though they are far apart. If the water comes into the media bed too fast or too slow, the siphon will not be engaged. The ebb and water height will be affected.

You need to set the Siphon in place and take it through a few operating times in the grow bed. Make some adjustments with the aquaponics bell to iron out the pump levels that control the water level in the grow bed feeding from the fish tank.

Bell Siphons are not only an integral part of the Aquaponic Bell siphon system but a fascinating feat of science.  The Aquaponics bell Siphon works to control water height in the grow bed and water level using a siphon bell pipe and aquaponics PVC bell to drain and fill a grow bed that contains grow media and plants.

With the ability to flood with water and drain a tank in a system with one pump greatly lowers the risks of failure. The siphon runs automatically and consistently giving the plants a stable growing environment.  By having even flood drain cycles, the plants receive even amounts of air and nutrients necessary for life.


How to Start a Cheap Hydroponic Indoor Garden:

  1. Start Seeds
  2. Seeds Sprout
  3. Transplant Seedlings to Container holding Water
  4. Mix the proper amount of Nutrients with water for the Roots of the Plants to Absorb
  5. Hang a Grow Light Above Container for Heat & Growth
  6. Maintain & Monitor your System
  7. Harvest .…………………………………………………………………………………………………………………………….. Read more



JimGalloway Author/Editor


Related Questions:

Where are bell siphons used?
A bell siphon is used in ebb and flow aquaponics and hydroponics systems in order to regulate the flow of water. In an ebb and flow, (also known as flood and drain) system, water is pumped into the grow bed. At a specific point (usually 2 inches below the surface), the water drains via the bell siphon.
What do you need for a bell siphon?
A bell siphon has three basic parts: a reservoir, a bell, and a riser. Here’s how it works: as water fills the reservoir, the surface of the water is equally exposed to atmospheric pressure.



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