DIY Outdoor NFT Hydroponics System

Introduction: DIY Outdoor NFT Hydroponics System

Hello friends. I am going to share with you my homemade NFT (Nutrient Film Technique) outdoor hydroponics system. I had wanted to start a hydroponics project for some time, and after a bit of research, I decided to go with an NFT system because it has several important features. As explained by epic gardening.com, its myriad benefits include:

  • Low water and nutrient consumption
  • Avoids need to use a lot of growing media
  • Easy to disinfect roots and setup
  • Easy to see root quality and health
  • Consistent flow prevents salt buildup in root area
  • Recirculating, so minimal groundwater contamination
  • Very modular and expandable

It's few dowsides are:

  • A failing pump can kill an entire crop within a few hours
  • Does not work well with plants that have large tap-root systems
  • Doesn’t do too well with plants that need a lot of support

Since I was interested in growing lettuce and other salad greens, which need little support and have small root systems, two of the three detrimental factors were moot, and long power outages are few and far between, so a failing pump hopefully will not be an issue.

The entire system was up and running in less than a week (only a few days worth of work) and cost me less than $200, and everything can be affordably sourced from either your big box hardware stores (namely Home Depot and Lowes) or your online everything vendor (Amazon and Ebay). It is modular, meaning you can add or subtract rows of pipe or length from each row, so as to tailor it to suit your own needs. So without further ado, lets get to it.

Supplies:

There are a lot of supplies to be purchased, but don't be daunted: all can be purchased for a total of about 200 bucks between Ebay, Amazon, and your local big box hardware store.

There are two main parts to this project: the frame, and the plumbing. For the frame, which measures 50 1/2" in height (without the caster wheels or manifold), 60" in length, and 48" in width, the materials you will need include:

Frame:

Lumber:

2x4s: 22'

1x1s: 20'

2x6s: 22'

Screws:

1 box of 2" 9 ga. for most of the connections, 1 box of 1&1/4" to screw the 4 horizontal 1x4 "flanges" to the 1x1 "webs" of the "T" beams. I used Deckmate exterior screws, which are coated to inhibit corrosion.

Corner braces and corner brackets:

Since the system depends on a rather specific slope from one end to the other, I braced all of the 90-degree angles that I could using brackets and braces to prevent sagging over time.

Caster wheels:

I used 4" caster wheels with a threaded stem. These were then mounted onto corner brackets, which were in turn mounted onto the frame.

Paint:

Used to help protect the lumber from the weather, as well as for aesthetics. You have some discretion here, but (assuming the system is set up outdoors) an outdoor paint is advised.

Plumbing:

Hydroponic Channels: 20' of 4" "Sewer Main" PVC (cheaper than standard "Schedule 40" PVC, the only difference (to my knowledge) is that it has a thinner wall than Schedule 40, and thus is not meant for pressurized applications. As this will be an "open system" (which does not operate under pressure), this should not be an issue.

Return manifold

10' of 2" PVC for the return manifold and return pipe (which flows back into the reservoir)

2 X 2" 45 degree elbow joint

3 X 2" 45 degree wye joints

3 X 2" 90 degree elbow joints

4 X 4" PVC flexible pipe caps

4 X 3/4" slip x slip bulkhead fittings

2" stainless steel pipe straps

Intake manifold

1 X 4-way garden-hose manifold (this should have a shutoff valve for each output, allowing you to select which channels receive water at any given time)

1 X 3/4" brass hose barb x GHT (Garden Hose Thread) fitting: mine is "male" thread (MGHT), but this may need to be female (FGHT) depending on which manifold you go with

4 X 1/2" brass hose barb fitting x FGHT

4 X brass dishwasher elbows (they have FGHT on one end, and a 90 degree elbow on the other)

1 X 10' length of 3/4" ID corrugated tubing (black): it should be black to prevent light from penetrating it, but will be painted white to keep it cool

1 X 5' length of 1/2" ID tubing (black)

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Step 1: Draw Out You Plans

Buy yourself some graph paper and make some drawings. It is much easier to have a separate page for each element with you outside (or in your workshop, etc.) than to be scrolling through a laptop. It is also advantageous to have a well detailed plan that you have made yourself, so that you will better be able to envision each piece and how they fit together.

Label each length of lumber with a circled letter {(A), (B), (C), ... etc. A few of these dimensions will be used for more than one (interchangeable) piece, so use the same letter for each identical piece. Make a list including each piece, consolidating like pieces [for example, you will want 6 horizontal 2x4s of 24", so if you label these pieces (A) on your drawing, your list will have: (A)-2x4 24" x 6]. Then you will know how many of each length you will need to cut.

Step 2: Gather Your Supplies

While the stuff that you have to order off of the internet will take a few days to arrive, you can get started with some of the elements of your system at your friendly local hardware store. I found the quality and price of lumber to be better at HD, while the PVC was cheaper at Lowes.

In order to best economize your lumber and reduce waste, you want to make cuts so as to either have enough left over for another piece that will be used, or have as little left over as possible. For example, for the lumber for the back vertical supports you will need 3 lengths of 2x4, one each of 46, 47, and 48 inches; this can all come from one 12 foot length, with only 3 inches left over as waste.

So for lumber, you will need:

2x4 x 12' (3 back vertical supports)

2x4 x 12' (6 horizontal supports)

2x4 x 12' (3 front vertical supports and 1 back horizontal support)

2x6 x 10' (3 diagonal supports)

Step 3: Cut Your Lumber/paint Your Wood

Most of the cutting is pretty straight-forward: the only somewhat-tricky part is cutting the notches for the horizontal pipe supports into the diagonal cross-bars. Use your saw of choice; I used my dad's adjustable miter saw. It is pretty much just a circular saw mounted inside a fancy frame which allows for cuts at precision angles.

Remember, the frame is meant to slope down from the intake to the outflow side, so all of the measurements for your vertical supports should reflect this slope of about 30:1 (30 horizontal inches for every inch of drop). Since my frame is 60 inches (or 5 feet) long, this gives us a nice even drop of two inches across the entire length. And since the second set of vertical supports is set halfway across, or 30 inches, this section will be exactly one inch lower than the first section at the intake side.

As for those tricky diagonal pieces, double and triple check the angles on the notches you'll be cutting out. Remember, these 2x6's will be at a 45 degree angle, so the notches cut out will likewise feature a right (90 degree) angle cut into the wood, and two 45 degree angles (or, rather, 135 degree angles), one at each corner leading to the 90 degree cut. I honestly can't remember the math or tools I used other than a T-square (since this is being written several months after the project's completion), but it's nothing too complex.

Plan your cuts ahead so as to best economize your lumber (leaving as little unusable length as possible), and sand down any rough edges after all your cuts are made. After all of your cuts are complete and you've finished (sanded) all the rough edges, you'll be ready to paint.

Painting is done for two purposes: to protect your lumber from the elements (assuming this apparatus will be spending its days outdoors), and for aesthetic concerns. My folks already had a theme going with all of their other backyard lumber projects (a couple pergolas and a fancy planting shelf) painted the same tone of red, so my choice was pretty much made for me. We had plenty of the blood-red paint left over, and since it was outdoor-rated, I was good to go. Two coats for better protection, took a good few hours (given the many pieces that needed doing), and it was done.

Step 4: Assemble Each Section

There are three of these diagonal support sections that need to be put together. Keep in mind, the second section should be one inch shorter than the first, with the third section two inches shorter than the first. Therefore, the upper horizontal 2x4 of the rectangular section will need to be 1 and 2 inches lower on the second and third section, respectively.

I used a Kreg mini jig for drilling "pocket holes," which conceals the connecting screws quite nicely, giving the final product a very professional and finished look. You can get the Kreg mini jig kit for 14 bucks on Amazon, and I'd highly recommend it. If you do decide to go with the Kreg, I'd suggest that you do one or two practice holes on a couple pieces of scrap wood, just to get the process down.

First do a "dry fitting," making sure all of your dimensions are right on. Then, using clamps, screw the bottom horizontal piece onto the (long) back vertical piece. Next, place the (short) front vertical piece onto the bottom horizontal beam, and screw it on in. Then do the top horizontal piece. You should now have a rectangle, with one end extending a couple feet in one direction out from the rectangle. Clamp the diagonal piece in place, and screw into the rectangle and the board extending from it. You should now have your first section complete.

Do the same with the other two sections, keeping in mind that they ought to be one and two sections shorter (in the vertical dimension). You should now have three nearly identical pieces (the only difference being that the second and third are one and two inches shorter, respectively).

Step 5: Make Your "I" Beams

These are fairly simple. All you are doing is taking a (painted) 1x4 and attaching a couple of sections of 2x2 or similar lumber along the length of the underside. You must do this in a couple sections because you want the bottom of the 1x4 flush against the vertical supports (so the 2x2 of the "I" beam runs between the vertical sections. Mark your 1x4 where the 2x2s will start and stop: you need to leave a couple inches "bare" where the 1x4 will rest directly on the vertical sections. Then cut your 2x2s to length, paint them, let them dry, and clamp them along the length of the 1x4s. You want to drill a pilot hole through the 1x4 into the 2x2 (preferably without coming out the back end), and then screw through the 1x4 into the 2x2. Use outdoor screws (I like deckmate screws, which are coated to inhibit corrosion).

Once you have your 4 lengths of 1x4 I beam complete, compare to make sure that the I beam sections are all bare in the same spots. These spots are where the 1x4s will drill directly into the vertical supports.

Step 6: Put the Frame Together

Now your frame will really start coming together. Stand up each of your three sections the appropriate distance apart; you will likely need to lean the three vertical sections against something to keep them upright (at first). Put your four 1x4 I beams into position, and drill drill drill. Make sure you use the appropriate vertical section in each place, so that it slopes slightly from one side to the other. Next, attach the horizontal 2x4s between each section

Build a couple rectangular frames for the doors out of 2x2 lumber (they actually won't be perfect rectangles, as one side will be slightly shorter than the other, to match the slope of the frame). Then affix shade cloth to the doors with "shade cloth staples" (don't cheap out and use regular staples: shade cloth staples are hammered in and attach the shade cloth more securely).

Now you will want to attach shade cloth around the bottom "box" section of the frame. This will help keep the reservoir shaded and cool (which is essential to prevent root rot), as well as allowing you to store supplies within mostly concealed (so there is an aesthetic component as well). A light colored shade cloth reflects most of the light (and heat), but allows the reservoir to stay somewhat ventilated (i.e. it won't "hot box" the rez, as a closed wooden frame would).

You can now attach the doors to the frame with hinges of your choice, just don't go with anything too flimsy. A couple door catches (pinch style or magnetic will work) will keep the doors from swinging open unexpectedly.

Now: caster wheels. This step is optional, but I found it a great convenience (both for moving the frame out to drain/clean the reservoir, and for wheeling the whole frame against the inside corner of the house last time a hurricane came 'round). I bought non-marring caster wheels (so they wouldn't mark up the ground) that have an integral threaded stem. Then, bought some stainless nuts with the same thread/diameter. I then drilled holes the diameter of the threaded stem in some stainless corner braces, and attached the corner braces in the places that I wanted the six wheels. Finally, I screwed one nut onto the stem, fed the stem through the hole in the corner brace, and sandwiched (backed) the two nuts tightly against each side of the corner bracket, thus securing the caster wheels in place.

Step 7: Prepare Your Channels (pvc Pipe)

Now you can go ahead and cut your 4 inch pvc pipe to length. I cut mine so that it extends just about 2 inches off the back (collection) end, and is almost flush with the distribution end (extending just about half an inch). Now you'll want to break out the hole saw bit and drill the holes for the net pots: I drilled the holes on 6 inch centers (the center of each hole 6 inches apart). I also staggered them, so that the holes of the top channel alternate with those of the channel below (the first and third pipe have the first hole 5 inches from the end of the intake side of the channel, the second and fourth have the first hole 8 inches in). This leaves room for the intake, which is a dishwasher elbow with a female thread connected to a brass nipple with a male thread.

When sourcing your brass (or plastic, etc. pieces: I found brass best, most cost effective, and easiest to source), make sure the thread is the same on the male and female pieces. I went with garden hose thread, which will be abbreviated either mght (male garden hose thread) or fght. The nipples I used are 1/2 inch/fght, meaning it has a nipple to accept 1/2 inch hose on one end, and female garden hose thread on the other. To install, just feed each piece through their respective ends of the 1 inch hole you've drilled, and sandwich the pipe between them and screw together. The dishwasher elbow should be pointed down the long end of the pipe.

Now get some rubber DWV pipe caps. Drill a 1 1/2 inch hole for the bulkhead fittings near the perimeter of the flat end, about 1/4 inch from the edge. Now sandwich the bulkhead fittings around the hole (after you've glued your corrugated pond tubing into the end of the bulkhead fitting with silicone caulking [the corrugated tubing is less likely to kink with the sharp 90 degree bend]). You may also want to paint the end caps/tubing white, to keep them cooler in the sunshine, thus preventing your nutrient solution from taking on heat. Make sure you leave enough corrugated tubing length to feed into the drainage manifold, which you will now assemble.

Step 8: Drainage Manifold

The drainage manifold collects the nutrient solution from the channels and feeds it back to the reservoir. All of the following pieces will be in 2 inch PVC. You will need 1x 45 degree elbow fitting, 3x 45 degree wye fittings, 4x end caps, and 3x 90 degree elbows. 10 feet of 2 inch pvc should do it. First, cut some 4 inch sections of pipe to attach the end caps to the top end of the 45 degree and wye fittings (note that the bottom wye fitting will be inverted from the other two, so that it accepts the pipe in line with the others, but drains 90 degrees from the ground - this means that the end cap will be placed differently from the other two wyes. Next, prep the surfaces of the fittings/pipe that will be glued with a very fine grit sand paper. Now use some PVC cement to glue the pipe into the wye, and then the cap onto the pipe that extends from the wye. You can drill a hole into the middle of the cap now to accept the corrugated tubing from the channels.

Now you will cut the pipe that runs between the top 45 degree elbow and wyes. Remember, measure twice, cut once: you want each drainage cap to be located as close to directly under each channel as possible (about 2-3 inches under, actually, so that you can bend the corrugated tubing a bit more gradually). Sand and glue each section in, making sure that they are all in line in regards to the channels. Again, the bottom wye is inverted so that it drains straight down.

Connected to the bottom wye is a 90 degree fitting that directs the pipe towards the back of the system, then another 90 degree elbow that directs the pipe towards the intake manifold end, where the reservoir will sit. Finally, one more elbow (with a short length of 2 inch pipe glued into it) will direct the flow downward into a hole drilled into the top of the reservoir. Run the pipe close to the wooden frame, so that you can use 2 inch pipe straps to support the pipe. You will also use these pipe straps (make sure that they are made of stainless or some other non corroding material) to secure the manifold to the side of the frame (which means that the manifold will be right against the frame: so you cannot have the output end of the channels extend past the frame at all).

Step 9: Grow Some Veggies

Your system is done, congrats! Now to grow some veggies. I start my seeds in rockwool cubes; once they've sprouted, I move them into a grow box with a mini DWC (deep water culture) system with LED lighting (soon to be the subject of another Instructable), which allows the roots to grow out into the nutrient solution/water. I also inoculate the roots with a mix of mycorrhizial (beneficial) fungi and bacteria (bought either online or at your local hydroponics supply store), to help keep them white and healthy (generally you need to keep the solution under 80 degrees F, but with mycorrhzae, you can push that up a few degrees without encountering root rot). Once there is enough root growth to reach the bottom of the NFT channels, I transfer them into the outdoor NFT system. If you do not feel like building a grow box, you can try an outdoor mini DWC system, ambient temperature permitting.

Well, there you are. I hope this how-to will help to inspire/instruct some of you to try your hand at home hydroponic gardening, which can be a fun, healthy, economical, and environmentally friendly pursuit. Any feedback is much appreciated. Cheers, and happy gardening!

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