Important Note: This design is the first version of the Do It Yourself Aeroponic System. The newer version is located here.
I've been thinking about building an aeroponic system from scratch for a while, and this week I gave it a first attempt.
The
garden has been largely dominated by the massive eggplant lately. The
eggplant itself is quite healthy, but it's a bad neighbor to everything
else in the TurboGarden. It's simultaneously crowding it's neighbors
and shading them under it's large canopy.
As far as I've researched, nobody is producing a single-site aeroponic unit. I thought it was time to make one.
I've spent a long time thinking about how to assemble an aeroponic
unit from scratch... I came to a few basic parts that would be
necessary, then expanded on the idea:
- A reservoir is needed
for the water. The reservoir should be some type of opaque material,
to prevent algae growth. Ideally, the reservoir should be easy to
monitor and service.
- In order to be an aeroponic system, you
need to have sprayers. These sprayers need to take water from the
reservoir and deliver it to the roots of the plant.
- The plant needs to be supported, and it needs to be kept safe from damage during water changes and maintenance.
I
started looking for my reservoir first. I considered lots of
containers, from the simple Home Depot bucket to more exotic
containers. I ended up choosing a dog-food container. Take a look at
the photo, and I'll start to explain why I decided on it.
I found a 40-pound size Vittles Vault,
made by Gamma Plastics. It's intended to be an air-tight container for
pet foods, but I had other ideas in mind. I liked the large
water-tight door, the generous capacity for water, and the flat top of
the container. It's naturally good at holding water, and is not prone
to leaks.
You're probably noticing that there's a bucket on
top... That's intentional. I decided to separate the reservoir from
the plant's "chamber". The bucket has been fitted to hold a 6" net
pot. The plant lives entirely in the bucket. Since the reservoir can
be seperated from the bucket easily, I can clean the reservoir without
disturbing the delicate roots.
How are they connected? Well, I
wanted to make a system with as few points of failure as possible.
Water likes to obey gravity, so in the chance of total failure, the
water can fall safely back into the reservoir. It's the path of least
resistance.
The bucket has a hole drilled through the bottom.
The reservoir has a matching hole drilled through the top. Take a
look, and it will make more sense:
That's
actually a "through-hull" fitting, it's used in boating. It's a sealed
"pass through" that leads directly down into the reservoir. This
serves as our water-return. The holes in both the reservoir and the
bucket were drawn using a simple compass, and were rough-cut using a
Dremel tool. They were then sanded using a small drum-sander to
achieve proper size and roundness.
Once the unit was dry-fit
properly, I sealed the "through-hull" fitting with aquarium sealant, to
ensure that it was totally water-tight.
The
lid of the bucket has been cut to accommodate a large (6") net pot.
The lid supports the weight of the plant, and the roots are able to
hang freely inside the bucket. Here's a top view of the bucket's lit
(and pot) for perspective:
Before we continue with construction, let's stop and talk about
aeroponics for a moment. Aeroponics describes a special breed of
hydroponics, where the roots of a plant are sprayed with an aerated
nutrient solution. To make a spray, we force water through small
jets. Luckily, these jets are pretty easy to obtain. I bought a
handful of them at my local hydroponics shop. In case you don't have
access quite as readily as I do, here's a link where you can buy them (please note, I have not done business with this merchant, and as such, cannot make any promises).
The
small microjets are threaded, and usually screwed directly into PVC
fittings of your choosing. Since nobody online seemed to know quite
what size they are, here's the final answer: The microjets are threaded to fit a 10-32 machine thread hole.
It's easy to make them fit into PVC. Simply drill a hole of
appropriate size, then cut the threads with a 10-32 tap. 10-32 is a
standard size (it's the fine-thread version of a #10 machine screw).
You should be able to buy a 10-32 tap quite inexpensively at nearly any
hardware store. Personally, I really like the Craftsman TapDriver.
It's a screwdriver-shaped handle that stores taps internally. It's
very convenient. Sadly, Sears does not have a good photo on the
website, so I've got no link to share.
You're able to construct
the supply lines for the microjets by simply using 1/2" PVC and
fittings. It's easy to cut and glue PVC, and it doesn't require a lot
of special tools.
Now that we know how we intend to supply the water; we need to know how we're going to get it there... We need a pump.
Here's
an important advisory for you about pumps. Don't just think you can
buy an off-the-shelf aquarium pump. I tried that. It didn't work.
Although
these pumps look convenient, they lack sufficient power to make the
jets work. A crappy pump will make your jets "dribble". You'll need a
proper pump to get them to the critical pressure.
After some searching and testing, I wholeheartedly recommend an ActiveAqua PU250.
The ActiveAqua brand is represented by Hydrofarm, and their pumps are
just what you need. Shockingly, the ActiveAqua pump actually cost me
less than the far-inferior pet-store variety.
Speaking
of pumps, the ActiveAqua PU 250 (and larger) pumps offer an important
and convenient feature. They have a pipe-thread connection to the
pump. Many brands of pump simply have a tubing "slip fit" connection.
I don't like "slip fit". It's not strong, and it's not reliable.
Threaded connections are much stronger, and they'll make your life a
lot easier. In this case, the PU250 has a 1/2" pipe thread connection for the "outbound" water. Here's a photo with the thread visible:
Ok... Now we've got all the ingredients together... Let's make it work.
I
wanted as simple a connection as possible, so I got an idea early in
the project: If I made the "return hole" in the bucket large enough, I
could pass the supply line for the jets through the middle of it
(meaning that I only have one hole to worry about instead of two).
This leads me to my sprayer system.
It's
a very simple setup. The pump shoots the water straight up a length of
PVC pipe. This pipe is capped at the top, and the only way for the
water to escape is through three microjets at the top. Here's a
closeup of the jets at the top of the pipe:
The
cap is just a regular 1/2" PVC cap. It's been drilled and threaded for
three 10-32 sprayers, which screw into it nicely. The PVC cap is
solvent-wended to the pipe to prevent leaks.
The pump rests
inside the reservoir, with the sprayer-pipe extending vertically. The
sprayer-pipe travels through the large "through-hull" fitting that
connect the bucket and reservoir, and stops just below the plant's
basket. Here's a photo of the whole thing assembled:
Also, just so you can see it from the top, here's another angle:
I
like this design a lot, as it's pretty simple. The water shoots out of
the sprayers, and is carried back to the reservoir by gravity. The
pump is always sitting in water. The whole system is designed to be as
leak-resistant as possible, while allowing for easy cleaning.
The
big "door" on the reservoir allows for easy access when you're testing
and adjusting your water. Additionally, you can completely disconnect
the bucket from the reservoir, should you want to do more extensive
cleaning. Since the plant never leaves the bucket, it's always
shielded from damage and accidents.
The
last part of the project was allowing the pump's cord to exit the
reservoir. I put the hole both as high as possible and as far from the
the "return" as possible, to minimize leak concerns. It's pretty
simple. I drilled a 1" hole through the reservoir using a hole-saw,
and fitted it with a large electrical grommet for a finished look.
Here's a rough estimate of the costs involved in building this aeroponic system:
- Small bucket and lid, $4
- Gamma Vittles Vault, $35
- ActiveAqua PU250 Pump, $15
- 1 1/2" through-hull fitting, $7
- Microjets, $2
- 6" net pot, $1
- PVC pipe and fittings, $3
Total
materials cost: Roughly $67. That's not bad, based on the costs of
commercial units. I bought all the parts for this project locally,.
The bucket and PVC were from Home Depot. The through-hull fitting was
from a boating store. The pump, microjets, and net pot came from my
local hydroponics shop. The Vittles Vault came from Petco.
You
could certainly lower the cost by replacing the expensive Vittles
Vault. Honestly, I just loved the easy access of the big watertight
door, and was willing to incur the expense for a nicer maintenance
experience in the future.
Admittedly, this was an experiment to
build a "large plant, single site" unit. In my next experiment, I'll
be looking at building a unit meant for several smaller (strawberry)
plants. If you have comments or questions about how this was
constructed, just let me know. If you have an improvement on the
design, make sure to share it with the group.