What Is a Bell Siphon and Why It Is Important in Aquaponics Systems

What Is a Bell Siphon and Why It Is Important in Aquaponics Systems

Proper drainage is very important in a media bed or flood and drain aquaponics systems, as excess water can cause damage to plants and fish. This is where a bell siphon comes in – a clever piece of technology that allows for efficient and effective water drainage in an aquaponics system. In this blog, we will discuss what a bell siphon is, how it works, and why it’s so important in media bed aquaponics systems.

Proper drainage is crucial in media bed aquaponics systems because it helps maintain a healthy environment for both plants and fish. Aquaponics systems rely on a delicate balance of nutrients and bacteria to ensure that plants and fish thrive. If the water in the system becomes stagnant or overloaded with nutrients, it can create an environment that is harmful to both.

Without proper drainage, water may accumulate in the grow bed, which can lead to water logging, root rot, and other issues that can harm fish and plant growth. Stagnant water can also reduce oxygen levels in the water, ammonia, and other harmful chemical build-up which can affect the health of the fish.

This is where a bell siphon comes in. It allows for controlled water drainage from the grow bed, preventing waterlogging and ensuring that the water in the system continues to flood and drain and remains fresh and oxygenated. The bell siphon also helps regulate the water flow through the system, which ensures that plants receive the nutrients they need without becoming overwhelmed by excess water.

What is a Bell Siphon?

A bell siphon is a simple yet highly effective device used in aquaponics systems to regulate water flow and drainage. It has several essential components, including a vertical standpipe, a horizontal drain, and a bell-shaped chamber. Water flows into the bell-shaped chamber, filling it up until it reaches the top of the standpipe. Once the water reaches a certain point, a vacuum is created that causes the water to drain rapidly through the standpipe and out of the horizontal drain.

This cycle repeats itself continuously as the water level in the grow bed rises and falls. When the water level in the grow bed reaches a certain point, it will trigger the siphon to drain the water out until the bed is at the proper water level again.

Benefits of Using Bell Siphon

  1. It helps regulate water flow and drainage, ensuring that the water in the system remains fresh and oxygenated. This promotes healthy plant growth and fish health. 
  2. A bell siphon is a low-cost solution that is easy to install and operate. Unlike other drainage systems that require pumps or electricity, a bell siphon relies on the laws of physics to work, making it a sustainable and eco-friendly solution for aquaponics systems.
  3. A bell siphon allows for the automation of water flow in an aquaponics system, freeing up time and energy for the operator to focus on other aspects of their system.

The Importance of Bell Siphons in Aquaponics Systems

If your media bed aquaponics system has no proper drainage the excess water can accumulate in the grow bed, leading to waterlogging, root rot, and other issues that can harm plant growth and fish health. 

Bell siphons play a role in regulating water flow and preventing flooding by allowing water to flow out of the grow bed when it reaches a certain level and then stopping the flow when the water level drops. This helps to maintain a consistent water level in the grow bed and prevents plants and fish from being overwatered.

Additionally, proper drainage facilitated by bell siphons allows for the efficient uptake of nutrients by plants. When the water in the grow bed is drained correctly, it creates a balance between the nutrients available in the water and the plant’s ability to absorb them. This balance is essential to ensuring that plants receive the nutrients they need to grow and thrive.

Instructions for Building a Bell Siphon

Building and installing a bell siphon for your aquaponics system is relatively simple. Here are some step-by-step instructions for building and installing a bell siphon:

  1. Gather the necessary materials – You will need a PVC pipe, elbow, cap, bulkhead fitting, and media guard (optional).
  2. Cut the PVC pipe – Cut the PVC pipe to the desired length, depending on the height of your grow bed.
  3. Install the bulkhead fitting – Install the bulkhead fitting at the bottom of the grow bed. This will allow water to drain out of the grow bed.
  4. Attach the PVC elbow – Attach the PVC elbow to the end of the PVC pipe. This will direct the water flow towards the drain.
  5. Attach the PVC cap – Attach the PVC cap to the other end of the PVC pipe. This will create the vacuum needed for the siphon to function.
  6. Install the media guard (optional) – If you use small media in your grow bed, you may want to install a media guard to prevent the media from clogging the siphon.
  7. Test the siphon – Fill the grow bed with water and observe the siphon in action. Adjust the height of the standpipe as needed to ensure proper water flow.

Proper installation and setup of the bell siphon are critical to its success. Here are some tips to keep in mind:

  1. Ensure the bell siphon is level and stable to prevent leaks and ensure proper water flow.
  2. Use PVC glue to secure all connections to prevent leaks.
  3. Test the siphon before adding plants or fish to the system to ensure it works properly.
  4. Keep an eye on the water level in the grow bed to ensure the siphon is functioning correctly.

There are also some common mistakes to avoid when building and installing a bell siphon. These include:

  1. Using a standpipe that is too short or too long can affect the efficiency of the siphon.
  2. Using a media guard that is too small can lead to clogs and reduced water flow.
  3. Overfilling the grow bed can cause flooding and damage to the siphon.


By understanding the essential components and workings of a bell siphon, selecting the right type for your system, and properly building and installing it, you can ensure the success of your aquaponics system. With a properly functioning bell siphon, you can enjoy the benefits of a sustainable, low-maintenance, and highly productive method of growing plants and fish.