More Bell Siphon Problems + Success With Dead Plants

Though my system seemed to be running perfectly, something has changed and everything has been thrown out of balance. I decided to look more into what effects the siphon and how I can fix it.

The bell siphon has 2 jobs:
1. Start draining the water
2. Stop draining the water

As simple as these tasks sound, it is a balancing act getting the components tuned. These components are:
1. Water flow
2. Width and height of stand pipe
3. Width and height of bell siphon
4. Cap on bell siphon
5. Down pipe

My siphon has trouble with both of the tasks its meant to do so I might as well start with problem #1. The siphon not starting is represented by your growbed filled with water to the top of the stand pipe. There is water dribbling out of the down pipe, however it seems to be leaving the growbed at the same rate it is entering and therefore the water level is not changing and something is preventing the siphon from initiating. If the siphon isn't starting, it can be due to the water flow being too weak. Other factors that can initiate the siphon is pressure from the down pipe. Elbows and restrictors increase the back pressure which helps the siphon action to start. There may also be an obstruction to the water entering the bell siphon.

I tried adding 2 elbows to my down pipe but it didn't work. I then glued 2 rubber O-rings into the pipe and threaded in a 10mm tube which will hopefully create enough back pressure to get the siphon to start.

If adjusting the water flow and down pipe doesn't seem to be working, you may have to revisit your stand pipe and bell siphon. Because my system was previously working, and I've put plants in my growbed already, I'm hesitant to touch these elements.

Today I got my siphon going again, however the process didn't stop which is represented through the water level remaining at the height of the slits in the bell siphon. The water again is leaving the growbed at the same rate it is entering and therefore the eater level isn't rising because the siphon isn't turning off. This is due to the same factors as above except opposite.

Reducing the water flow will lower the amount of water entering the grow bed so the siphon can fully disengage and the flooding can start again. Reducing back pressure in the downpipe by getting rid of elbows can also work.

Read more: http://www.japan-aquaponics.com/bell-siphon-guide.html

I am yet to perfect the system that will work day in - day out, however there is good news! The (almost) dead thyme plant has grown new sprouts which shows that the aquaponics system is doing its job. I also bought 4 new fish but I think that the first fish is getting bullied now.

Experiment with Dying Plants

I have some herbs growing in a normal pot with soil that lives on a window sill inside my house, however, the basil and thyme plants are dying.

I decided to take them out of the soil pot and move them into my Aquaponics system to see if any live can be brought back to them.

Introduction of Fish

Once the system was working 100%, I thought I should add the fish. I was warned that I might kill a few fish in my aquaponics exploits so I purchased some extras to ensure it was as unlikely as possible.

Shopping List:
1 Goldfish
pH Testing Kit
Water Thermometer

The pH level of the water was too far on the alkaline side and so I added the powder to bring the pH down and make it more acidic.

The pet shop recommends the goldfish don't live in water that gets below 15 degrees celsius, however the lowest I have measured so far is 12 degrees and the fish is fine.

Planting the seeds didn't work out, especially because I had to take all the pebbles out to fix the water flow. I bought a strawberry plant and recommend any seeds used are germinated externally.

System Not Working

I've been having a problem with the system and as a result the water is draining out at the same speed as the water is being pumped in. After trying a few things I decided that my water flow was too high and the draining wasn't happening rapidly enough.

I thought perhaps there was a leak in the system as my male and female fittings didn't fit tightly enough. I decided to cut about 5mm off the end of the male part so that with the rubber o-rings the area was 100% watertight. I also used a wrench to ensure they were secure.

To draw the water out more quickly, a long down pipe is needed. I made the down pipe approximately twice as long which helped the water leave the grow bed more rapidly. My cat agreed.

Secondly. I changed the tube that was coming from the pump. Though it was recommended I use a 12mm tube, I've switched it for a 9mm tube which means the water will enter the grow bed much slower giving the siphon a chance to draw all the water out and to not get stuck in a cycle.

The last problem was that with recent rain in Sydney, the water in the fish tank was getting too high and the bottom of the down pipe was being submerged. This meant the siphon action wasn't cutting off properly and the issue mentioned earlier was occuring again. I've moved the system undercover to avoid rain making the water levels unbalanced.

Plants!

Now for the fun part!

After looking through many articles on what plants to use when, I ignored all of the information and went and bought parsley and mint. I also bought strawberry, cucumber and tomato seeds. In retrospect I probably should have let the seeds germinate before planting them but we'll see how they go.

Carefully remove the plants from their pots and wash all the soil off their roots. This system doesn't use soil and it can clog up the tubes.

Make a hole deep enough to reach the water level and cover the roots of the plants. The seeds should be planted at the depth specified on the packet.

Let the plants filter out any impurities in the water before adding fish.

Testing the Bell Siphon

Once your grow bed is set up, it is important to check the bell siphon is working and that the stand pipe is at the correct height.

Using a semi-transparent grow bed allows you to see the height of the water rising which helps to callibrate everything.

Initially use a high water flow to check the siphon is working, but once it is set up a slower water flow can be used. Once the grow bed fills to the top of the stand pipe, water should start dribbling out of the down pipe. Depending on how much optimisation and experimentation you did with your bell siphon effects how quickly the siphon action takes to kick in.

The water will start to drain rapidly and once the water level reaches the highest slit on your bell siphon, this process will stop and the grow bed will start filling again.

Letting this cycle occur a few times will also wash any residue left on your gravel that could potentially clog the system or poison your fish and plants.

Making the Grow Bed

Once you have a suitable container for your grow bed, measure the depth of the gravel. Learn from my mistake and measure the types of gravel separately to save yourself from sorting them again later. Make sure to shake the container to ensure the gravel has settled before measuring.

Cut your stand pipe to a length 25mm - 35mm below the depth of your medium. The pipe used here has a flared ending which makes the draining process more rapid.

Drill a pilot hole into the bottom of the grow bed in the position you want your stand pipe. Use a spade bit to increase the width to the thread diameter of your fittings. Sand away any jagged edges.

Place the male fitting with a rubber o-ring into the bottom of the grow bed and secure it with the female fitting and another o-ring on top.

Cut a length of PVC pipe around 30mm longer than your stand pipe. Mark out slits in the bottom of the pipe and use a sharp saw to create a groove. Widen the groove using a saw with a larger blade.

Using the elbows and more of the pipe to create a downpipe with a bend. More length will ensure the water is drained quickly from the grow bed.

Fit the standpipe, bell siphon and down pipe into the grow bed. Add the bigger gravel first to secure your bell siphon and add the smaller pebbles on top.

Understanding the Bell Siphon

Plants receive the most amount of nutrients and oxygen through slow flooding and rapid draining of water into the growbed. The water leaves the grow bed through a stand pipe and the rapid draining is achieved through a bell siphon. If the water was to leave the grow bed at the same rate it was entering, the roots of the plants would be continuously submerged in water and cause them to rot.

A bell siphon uses atmospheric pressure to control the rapid draining of water. A liquid always flows from an area under higher pressure to an area of lower pressure. The water flows up the bell siphon (an area of lowered pressure) and into the stand pipe, again lowering the pressure at the top of the tube.

Once the flow has begun, it will continue if undisturbed as long as the inside end of the tube remains below the surface of the liquid. The flow can be cut off by raising the outside end of the tube above the level of the surface of the liquid in the container.

The top of the stand pipe should sit around 25mm - 35mm below the surface of the medium. This will ensure the top of the medium stays dry and no insects or pests are attracted. The top of the stand pipe is how high the water will get to before the siphon is activated and it is drained out quickly. The highest slit determines how much water will be left in the grow bed once the siphon cuts off. 

More rapid draining can be achieved through a stand pipe that has a wider opening at the top. The downpipe also affects how quickly the water is drained. The configuration showed in the diagram below is one of the most effective ways of quickly activating the siphon.

Using a bell siphon over an electrical timer reduces the amount of parts using electricity and which can malfunction as well as applying physics in all its glory.

Getting Started

This blog is about building an aquaponics system with no prior experimentation or hands-on experience into growing plants. After watching hours of YouTube videos and scouring the internet for a simple way to make this system, I decided to give it a go myself.

Fish produce high-nutrient water that will eventually kill them if not cleaned. Plants need nutrients and have the ability to filter water. These ideas are combined in aquaponics which utilises these benefits to produce a highly productive and low maintenance farming process.

What I used:
- Grow bed
- Fish tank
- Pump
- Tubing (diameter depending on what fits the pump)
- Smaller river pebbles
- Medium-sized rocks
- PVC pipe 48mm outer diameter
- PVC cap 48mm inner diameter
- Pipe 22mm outer diamater
- PVC elbow 22mm inner diameter
- Male/Female fittings 22mm inner diameter
- 2 rubber washers 22mm diameter
- Drill with 2mm drill bit
- 20mm spade bit
- Cat