U Siphon For Aquaponics – Is It Better Than The Bell Siphon?

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Last Updated on January 31, 2023

A U siphon for aquaponics can be an excellent mechanism for efficiently draining your grow beds and ensuring that your system remains healthy. The bell siphon has traditionally been used in aquaponics, so you are probably wondering whether the U siphon could be better than the bell siphon. You will find out the answer to that question in this article, keep reading.

What is The Purpose Of a Siphon?

The basic use of a siphon is to drain water from a grow bed conveniently without having to disconnect the pump. The added advantage of this is that during the siphoning process, nutrients remain available to the plants and the rapid movement of the water ensures that there is a high supply of oxygen in the water and the roots can uptake it.

The process of siphoning may look mystical, but it actually uses the natural law of gravity to suck up the water and expel air from the pipe until all of it is out, and then the water flows out.

Different types of siphons can be used. Because of the choices that are available and the different opinions around them, it can be pretty confusing. Two common types of siphons are used in aquaponics, the U siphon and the bell siphon. Let us get a good understanding of both mechanisms and make a decision.

U Siphon vs. Bell Siphon

The U siphon is convenient, very easy to install, flexible, and can be adjusted as needed. You can install a U siphon internally or externally, making it versatile. The one problem with a U siphon is that it can be quite difficult to fix. So you need to understand the mechanisms of how it works if you are going to do so.

The bell siphon is commonly used by many growers. It however requires some effort. The bell siphon functions as a single unit, limiting the number of moving parts required. The mechanism of this siphon uses gravity and pressure to drain water and will maintain a minimum volume of water in the tank it drains.

The main difference between the two siphons is the installation. The U siphon is quite easy to install and flexible. The bell siphon can be faster and has great draining abilities but it can be difficult to install and prime. It may cause trouble even for experienced users.

A better understanding of these two siphon methods will allow us to decide which to go for. Therefore, let’s dive into the mechanism of the U siphon and the bell siphon.Mechanism of U Siphon for Aquaponics

Mechanism of Bell Siphon for Aquaponics

The bell siphon lets water fill up inside a grow bed. After the water has filled up, the bell siphon drains out water from the grow bed. Bell siphon always sustains a moderate water range and drains excess water back into the reservoir.

The bell siphon operates automatically. It saves you the hassle of manually turning on and off the pump of the flood and drain process. Here is how it works:

  • Stage 1 (Filling): through the water inlet, water floods continuously into the grow bed filling it up from the water pump.
  • Stage 1 (Water lock): when the water fills up the stand siphon pipe to the point of overflow, water begins flowing down through the drain tube and forms a water lock. By this time, the air left in the cup has been sucked out.
  • Stage 3 (Drain): water now drains or flows out of the grow beds. Water from the cup is now sucked out after draining water to a particular level.
  • Stage 4 (Breaking siphon): now as the water drains out and drops down to the level of the bottom siphon pipe, air enters inside. This relieves or breaks up the siphon pipe pressure and stops the drain of water.

Aquaponics Auto Bell Siphon Kit 6″ Media or Smaller Grow Bed Mini Garden

This process keeps on going by filling water into your grow bed and siphoning it out. The flood and drain process continues for an unlimited time except when the pump is stopped.

Mechanism of the U Siphon for Aquaponics

As we mentioned earlier, the U siphon is very easy to install unlike the bell siphon making it a great option for beginners.

The main component of the U siphon is the PVC pipe that drains your growing bed. U siphon pipe has an angle of 45, 90, 90, and 45 degrees elbow and a straight pipe. The adjustable U siphon PVC pipe brings in water and the water level does not exceed the loop height.

The U siphon supplies water in and out of your grow bed. When the water level in your grow bed rises, the water level in your U siphon also rises. The curvature end of the pipe contains air. With the motion of water, this air is drawn out and it activates a suction effect.

Once the level of water gets to the loop or curvature of the U-shaped pipe, water flows out and siphons out by the suction effect. Now your entire grow bed drains out rapidly from the elbow through the siphoning process.

Read more about Best Plants for Small Aquaponics

How to Make a U Siphon F0r Aquaponics

The primary material you need is PVC piping. To install the piping, you will need to:

  1. Drill a hole right at the bottom of the grow bed. You will then need to use either a threaded PVC or hose adapter to make sure that this hoke is tightly sealed. The pointed end of this implement needs to stick outside the grow bed.
  2. After this is done, you will use the PVC pipe to create a loop. The height of this loop will determine the maximum height of the water level, so remember to consider this when making it. make sure that the loop leaves some space between the loop and the top of the grow bed. For a more detailed step-by-step process on how to make a U siphon, you can watch this video.


The use of a U siphon in aquaponics is also referred to as loop siphon aquaponics. This is because of the shape of the siphon. The loop works in a simplistic and automatic, and is used for drain ebb and flow hydroponic systems. As the water rises in the grow bed, the water in the loop also rises.

The aquaponics siphon drain is brought up to where you want the water level in the grow bed to be and then brought back down to the water reservoir. The shape resembles an inverted U shape, hence the name “U siphon”. The U can be squared or rounded at the top, it is up to you to decide on the shape you want.

Conclusion – U Siphon For Aquaponics 

There you have it, the comparison between the U siphon and the bell siphon for use in aquaponics systems. The bell siphon is commonly used and easy to understand how it works, however, it can present challenges with installation and priming which can cause significant problems such as flooding if you need to drain your grow beds.

The U siphon on the other hand is quite simple to install and use, once it is installed properly it will automatically prime itself and will drain your grow tanks to where you want the water level to be.

When it comes to aquaponics, for your fish and plants to receive sufficient nutrient quantity, it is important to achieve and sustain the right continuous flow of water. A siphon (be it U or bell siphon) is responsible for this. It is used to drain grow beds and it controls and balances the flow of water throughout the system.

The draining process of siphoning allows the availability of nutrients for your plants. It as well facilitates root absorption of oxygen which will help your plants grow excellently well. A U siphon may b the better option of the two.


How do you make a bell siphon for aquaponics?

The bell siphon is the device that takes water from the bottom of the fish tank and transfers it into the grow bed.

The first thing that comes to mind is a simple water trap (e.g. see this). You can use a similar design, but with a bigger hole and a larger diameter pipe to get the water out of the tank. Then, you'd have a small chamber where the bell siphons.

Making a bell siphon for aquaponics is not as easy as you might think. The first problem is that the shape of your tubing determines how much water will flow through it. You need to choose a shape that allows for more water flow than you need to run your system. If you are designing your own, you will have to calculate how much flow you need to run your system, and then design your tubing so that it can handle that flow.

The second problem is that the diameter of your tubing has to be chosen based on the amount of flow you want. If you have a garden hose with a 5/8" diameter, you can't run a garden hose with a 1/2" diameter through it without clogging it up. There is a point where your tubing will have to get smaller than the size of the hole in which it is installed, and this will make it impossible to run a continuous stream of water.

How do I install a bell siphon for aquaponics?

If you have a bell siphon already, and want to add a bell siphon, you should be able to just follow these steps:

1. Take off the old siphon. (You can do this with a pair of pliers.)

2. Take off the top half of the old siphon. (This is the part that will go into your new bell siphon)

3. Make sure there is no water in the old siphon.

4. Make sure that the bell siphon has no holes or cracks in it.

5. Make sure that the bell siphon has a hole that fits perfectly into the bottom half of the old siphon.

6. Put the top half of the old siphon back on.

1. Place the new bell siphon over the hole in the bottom half of the old siphon.

2. Fill the bell siphon with water.

3. Put the top half of the old siphon back on.

4. Put the lid on the bell siphon.

5. Make sure there is no air inside the bell siphon. (Air will make the bell siphon not work.)

6. If you put a little dish soap in the water, it will help to clean out any water or sediment from the bell siphon.

7. If you use a lot of dish soap, it can get into the siphon. Then, it will stop the bell siphon from working.

8. If you do not want to use dish soap, just turn off the water in the kitchen sink and let the water sit in there overnight. The water will clear itself out.

9. Turn on the faucet and slowly turn on the water. (You may need to turn on the cold water first.) This will make sure that the bell siphon does not get clogged up.

10. When the water is at the right temperature, slowly start turning on the water to fill the bell siphon.

11. Wait until the water is full.

Which is better U siphon or bell siphon for aquaponics?

I have a 10 gallon tank with about 6 plants in it. I'm new to aquaponics and am wondering if I should get a bell siphon (which will be used for the water flow) or a u siphon (which will be used for my fish). I've looked at other aquaponics forums and most people are using a bell siphon but some are saying that a u siphon is better. What's the difference between the two?

The bell siphon has a long neck that connects to the tank while the u siphon has a short neck that connects to the tank. The bell siphon is for the water flow, and the U siphon is for the fish. If you only have one of those, you will have to find some way to do both. 

The answer depends on how you are going to use your system. If it's just a hobby, then probably the U siphon will be fine. However, if you are looking at commercializing your system, I would go with the bell siphon as it allows you to add more fish.

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