In my previous post about the aquaponics system I’ve built, I mentioned something called a “bell siphon”, and called it magic. In truth it is simply science, but works so well and does so much with a very simple setup, that it may as well be called magic.

What it does is allows water to fill up to its top, then drain the water down to the bottom of the stand by creating a self-starting siphon that allows self-terminates. As the growbed is continuously filled, the bell siphon allows the water to be intermittently dumped into the fish basin below. This gives the plants both a period of water plus nutrients and a period of air for their root systems to allow optimal growth in the soil-less media.

And since the bell siphon requires a pump to run continuously, no timer is needed, and the pump tends to have a longer life, since starting and stopping will shorten a motor’s life.

Just kick it off and watch it go, just like this:

Blue is water, being pumped in from the top right. The green and yellow lines represent the bell siphon.
As the water fills up, it starts to overflow into the drain pipe (green) causing a siphon to start, draining all of the water to the bottom of the bell. Since the water continuously fills, it is a constantly repeating process.

The Build

I researched bell siphons for several days before stumbling onto something that made sense to me (and wasn’t in metric measurements). This is the video was what I ended up using as the guidelines for building mine:

My materials list for my bell siphon setup (listing is for one setup):

• 1 – 3/4 slip x male threaded (one half of the through fitting)
• 1 – 3/4 slip x female threaded (the other half of the through fitting)
• 1 – 3/4 x 1 inch reducing coupling (this is CPVC, but don’t worry, we won’t be putting any pressure on it)
• various lengths of 3/4 PVC pipe, roughly two feet total
• 2- 3/4 elbow
• 1 – 2 inch PVC cap
• 2 inch PVC pipe at least 12 inches long to be cut to length later

 Assembly

1. In the bottom of your grow bed, drill a 3/4 hole. Insert the 3/4 slip x male threaded in through the top. Attach the 3/4 slip x female threaded, using a washer, gasket, or “O” ring is suggested to prevent leaks. Mine leaks, but the leaking water drains back into the fish tank, so I don’t mind.
2. Insert a short piece of 3/4 PVC pipe into the 3/4 slip x female threaded fitting on the bottom of the grow bed. To the other end, add a 3/4 elbow, another short run of 3/4 PVC pipe and end that with another 3/4 elbow. Be sure to direct water flow back into the fish tank.
3. Inside the grow bed, insert a short piece of 3/4 PVC pipe, and then the 3/4 x 1 inch reducing coupling on top. Keep in mind that the top of this is the depth the water will go to before draining. Adjust the pipe length to adjust the height the water goes.
4. Make the Bell Cover. Cut a piece of the 2 inch PVC pipe about 1/2 inch taller than the height of the part made in Step 3. On one end, cut slice witha saw, drill holes, or cut out gaps to allow water to flow in. Keep in mind the highest cut in the this pipe will be the lowest point the water will drain. On the other end, place the cap. Slide the entire unit over the stand pipe.
5. Alternatively, place a larger piece of PVC to act as a strainer, in this case a 4 inch piece of drainage pipe would fit perfectly. Simply cut it tall enough to match the height of the bell cover, make sure it has plenty of perforations (saw cuts, holes drilled, etc) that allow water through, but keep out debris.
6. Pump water in to test.

The parts you will have to tweak will be the height of the stand pipe, and the height of the cuts in the bell cover. Adjust according to the depth of your media.

Tomorrow, I’ll cover the power plant I set up as part of the project, the solar panels, charge controllers, and batteries.

Peace,
db