Critique of planned Aeroponic system

19 years ago

I am interested in building an aeroponic system.

I have seen plans for using rubbermaid containers, pvc pipe, or square vinyl fence posts, while using inserts such as solo cups or net pots. I would like to use a round 6" pvc pipe, with pvc inserts of 3/4" - 1" to surround the stem. This system will be outdoors in full sunlight.

I am considering two separate ten-foot lengths. One will have cucumbers next to a trellis, and one will have roma tomatos and bell peppers. One 32 gallon reservoir will supply both sections. The reservoir will be several feet away in the shade, and will have a rio 1400 submersible pump. The large pipes will be elevated as little as possible while still draining back into the reservoir.

To provide the fine aeroponic spray, I can only think of two options. One would be to use micro-irrigation tubing and misters laying inside the pipe. The other is to drill several fine holes in a length of 1/2" pipe, and lay it in the bottom of the 6" pipe. The thought is that the water pressure will create a needle-like spray which will splatter on the inside walls of the larger pipe.

I have a 15-minute lamp timer, and plan on 15 minutes ON and 15 minutes OFF during daylight hours. I am not worried about power outages.

My immediate concerns are:

Will the roots clog the pipe or interfere with the misters to the point of failure?

Can nutrient solution be sprayed through common micro-irrigation misters for weeks or months without salt buildup?

Can a 420gph submersible pump create enough pressure to operate misters or create the needle-like spray?

Do I need to run the system during the night?

This will be my fourth year with a hobby hydro garden. I have tried the 2-liter soda bottle ebb and flow, and rain gutters filled with perlite. I have always had decent results and learned new things. I am as interested in building new systems as I am with growing plants. As this is a hobby, I am not too concerned with maximizing yield, tweaking EC, TDS or such things. I would just like for it to work and produce a few vegetables while being cheap enough to buy supplies at the hardware store.

I am seeking advice from others who have tried similar systems, or to point out obvious problems that I may be overlooking.

Thanks in advance,

-petunia sunshine

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Comments (18)

tony_k_orlando
19 years ago
I can assure you the roots WILL in fact clog the tiny holes in your spray pipe. It happened to mine.

The fix is to mount the spray pipe above and have them spray downward or any direction you like, just keep the pipe up above the bottom.

This should solve your problem with roots.

Another problem is debris clogging the spray holes. Having the pump in a filter like box or nylon sock AND the return being filtered too will delay the clogging, but it will most likely happen someday.

Fix is to drill more holes than needed to assure there will always be a spray OR engineer some sort of sprayer that can be removed , cleaned and reinserted. Again, mount on the top.

good luck

Tony
willardb3
19 years ago
Nutrient salts are a pain in the butt with high pressure drop emitters and they will clog eventually, in the 1-2 mos range depending upon how rich you run the nutrient.

Pumps come with a chart that shows how much volume a pump will do at how much head. 420 gph is irrelevant without head capacity as well. In that misters have high pressure drop, it is important to find out if your pump will overcome the change in elevation + emitter pressure drop in ft of head.

I have experimented with running pump only when lights are on (16 hr/day) or 24 hrs/day and cannot notice a difference in plant growth.
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hank_mili
19 years ago
The Rio 1400 has a max head of 6.5 ft. to low for an irrigation mister. I had an idea of using an ultrasonic water fogger instead. A five transducer fogger uses about 500 ml/hr. Just a thought.
chefmichel
19 years ago
Aeroponics seems to be the "dream" of every hydroponic grower,
however, one has to remain realistic and stay into the realm of the possible. You will need a high pressure pump, and need to watch the emitters very closely. Maybe replace them preventively every 1 or 2 months. The BIG question; is it worthwhile ?
I prefer to work with the KISS option, Keep it Simple.
I irrigate from the top, by using 1/2" all the way, then
reduce the flow with modified black stool rubbers. [URL=http://img.photobucket.com/albums/v309/chefmichel/hose_feed.jpg][IMG]http://img.photobucket.com/albums/v309/chefmichel/th_hose_feed.jpg[/IMG][/URL]

[URL=http://img.photobucket.com/albums/v309/chefmichel/Stoolrubbers.jpg][IMG]http://img.photobucket.com/albums/v309/chefmichel/th_Stoolrubbers.jpg[/IMG][/URL]
chefmichel
19 years ago
Sorry, here the pictures of the stool rubbers.
You insert it in the 1/2" water hose. Of course, you need to drill holes or slice them, for the water to flow. This is a cheap and effective alternative to misers. I hope my explanation is clear enough.
baci
19 years ago
As a general guide, pressure (psi) is about half the lift. I built some of the home systems using sprinkler emitters, & they constantly clogged with the nutrient salts.
willardb3
19 years ago
Actually, psi = 62.4/144 = 0.433 psi/ft head or, the inverse, 2.3 ft head/psi
baci
19 years ago
Great pictures, Chefmichel. I finally understand what you are doing with your system. You have such clever ideas.

Willard, I was trying to figure out your formula, & this is what I came up with:

Pressure (PSI) = Force/Area (square inches) or F/A
F = force (lbs.) of water = 62.4 lbs./cubic ft.
A = area of 1 cubic ft = (144 square inches)

P = F/A = 62.4 lbs. / 1 sq. ft. = 62.4 lbs. / 144 sq. in. = .433 psi

Which is what you said:
psi = 62.4/144 = 0.433 psi/ft head

So to figure out the psi when given ft of head, it looks like it is .433 divided by ft head. I thought it was .433 times foot of head, but maybe I have it backwards. Also, do the ft head need to be converted to inches?

Another question. I have returned some pumps because I felt their lift was not what the package said. I am wondering if the psi for pumps is measured at some standard elevation. I am at about sea level, & after reading this post, I am guessing I should expect less of a lift than those at higher altitudes.
willardb3
19 years ago
Density of water at sea level and 70F temperature is 62.4 lbs/cu ft

Force exerted must be converted to inches and there are 144 square inches/square ft

62.4/144 = 0.433

Sea level and 70F are considered standard conditions at which pumps are rated. Density changes with altitude and temperature.

Less pressure at altitude will cause pump cavitation sooner than at sea level, so, at the same head, pump will pump more at lower altitude.
baci
19 years ago
Thanks for your patience & explanations, Willard. You wonÂt find this kind of information on most hydro forums.
After re-reading some of these posts, it looks like the problems I had with my aeroponic systems involved my choice of emitter. It looks like some growers had had good success with the low head pumps by making their own or choosing an alternate emitter. I will try these again before purchasing the expensive items.
But, just for my own clarification, if I ever purchased a 70 psi sprayer, & there is 0.433 psi/ft head, it looks like I will need 70/.433 or about 162 ft head. (This is ignoring other factors such as tubing distance, etc). Is this right?
willardb3
19 years ago
snip
But, just for my own clarification, if I ever purchased a 70 psi sprayer, & there is 0.433 psi/ft head, it looks like I will need 70/.433 or about 162 ft head. (This is ignoring other factors such as tubing distance, etc). Is this right?
snip

Ayuh..... that's correct. Be careful of ignoring pressure drop in tubing/piping as sometimes the head (pressure drop) is higher than you think.

See my other post for low pressure emitters and their source.
hank_mili
19 years ago
Here's way to get a fine mist without a pump.
You will need:
1. Irrigation controller.
2. Solenoid valve.
3. Inline fertilizer feeder.
3. Pressure reducer.
4. 1/4 in. tubing.
5. Mist head emitter.

The feeder can mix fertilizer at a ratio of between 1/2000 to 1/50.
The mist head will need about 20-25 psi in order to get a nice foggy mist.
The big down side of course is that this system is open. But I guess you can still collect the runoff and use it somewhere else.
baci
19 years ago
Thanks, Willard, for your clarification. I have seen your other post & have kept the information you provided me on pressure drops before. It helps for me to learn complicated things in segments; & then hopefully later put the whole picture together. The emitter you use is very inexpensive, which is nice. All the information is very helpful, & I am going to try again.

Hank, I am a little unclear about your idea. How do you get 20-25 psi to your system without a pump? Is your emitter rated for that psi? Will any solenoid valve do, & do you have some sort of diagram?
hank_mili
19 years ago
Sorry if I was unclear. The source of the water pressure comes from your local water supply line that runs about 40 - 60 psi. From the water outlet we connect a generic irrigation solenoid valve that is controlled by an irrigation timer, attached to the valve is an inline fertilizer (nutrient) feeder, and attached to the feeder is a pressure reducer which drops the pressure down to about 25 psi. Now from the pressure reducer we connect a 1/4" fitting for the tubing, the length of tubing goes to the top of the 10 ft. PVC pipe that Petunia proposes for her design. At the end of the tubing we attach a mist head or in the case of Petunia's design we put a T-coupler and run two lines to her two vertical PVC pipes. The mist emitter sometimes called a fogger needs about 20 psi to generate that fine mist with the smallest droplet size. Hope this helps some. I'll try and draw a diagram and post it later.
hank_mili
19 years ago
After doing some more research on mister/fogger emitters there are some out there that can handle 35-80 psi. So in the design I suggest we can eliminate the pressure reducer.
baci
19 years ago
Thanks Hank, for your explanation. It gives me a clearer idea of what you are trying to do & I have learned more about psi in the process. I have found all the ideas adaptable do different systems of mine. I have one system with a higher psi water pump that attaches to a garden hose. I think I can adapt the stopper idea above will work for that system.
petunia_sunshine
Original Author
19 years ago
Thanks to all members for your responses. I have learned a few things. One, is to place my emitters at the top, spraying down, rather than at the bottom, spraying up. Second, is that misters will no doubt clog. Third, is to look into fertilizer injectors.

I like the idea of a solenoid and fertilizer injector. I have seen pics of injectors before, but have not pursued them as they are not available at stores such as Lowe's / Home Depot.

I believe that if I calculate the numbers correctly, I should be able to use 1 or 2 five gallon buckets of nutrients, injecting into the main irrigation line.

In my non-hydro ground and container garden, I use micro-irrigation sprayers and drippers, which are controlled by a lamp timer and "Rainbird" automatic sprinkler solenoid valves. I encourage those who are interested in DIY automation to look into these solenoids, which cost about $12-$15. The hose faucet is always on, but the solenoids only deliver the water when the lamp timer instructs them, in 15-minute intervals. Last year, I watered my plants 15 minutes each morning and 15-30 minutes in the afternoon.

Using an attachment to dispense fertilizer seems to be an easy way to convert this for hydro use. Runoff can be collected for watering other plants.

My previous container and ground system, in simple terms, has been:

WATER
outside faucet -> 25 psi regulator -> tubing to solenoid -> solenoid -> to all micro-irrigation downstream (misters, drippers, sprayers, etc.)

ELECTRIC
(Indoors) 110V GFCI Outlet -> 15 Minute Lamp Timer -> AC-DC Adapter (at least 1 Amp) -> (Routed through window to outside) Direct Burial Wire -> Solenoid

This was a DIY project in which I believed I took necessary safety precautions. Please consider safety first when using electricity near water, whether indoors or out.

I welcome all criticisms and suggestions...

-petunia sunshine
jebradl
19 years ago
You might consider using micro sprinklers. I have a system (a rubbermaid container type, which has micro sprinklers with a Rio pump) which in over a year's usage, has never had the sprayers get plugged (and I don't have a filter in place).

Critique of planned Aeroponic system

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