The Encyclopedia Hydroponica

Your Hydroponics Compendium

My Quick and Dirty DIY DWC 23 May, 2008

Filed under: Blog — E.H. @ 12:25 am
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Okay, the basic concept of DWC (Deep Water Culture) hydroponics is pretty simple.  You have a container of water with nutrients dissolved in it, plants suspended above with their roots down in the water, and a nice vigorous amount of air bubbling up from the bottom.  Roots get water, food, and air, just like they need.

To this (as with any hydroponics or other indoor growing situation) you need to add light and air.  Air you say?  Why your house is just full of the stuff isn’t it?  Sure, but plants like a breeze, so you need to provide it.  ESPECIALLY if you’re growing indoors since the lights involved are of the “ohmigawd my eyes it burns it burns my eyes” variety.  You’re going to want something opaque between you and that kind of light, which means that air doesn’t go through it either.  (Things that stop light stop air.)  So there’s got to be some way to get fresh air into this enclosed space.  Plants need to breathe too.

Let’s take a look at my “finished” product.  I put finished in quotation marks because I’m a tinkerer.  Things I build myself are only as finished as my next idea for a modification.


You’ll melt the tubs and probably start a fire or something.

Now if you remember the DIY Earth Box I made for my mom you’ll remember I had a left-over part – about 2/3rds of the top of a gray rubbermaid bin.  You can see it in the middle of the structure here.  (It’s upside down and jammed into the top of the blue bin.)  It’s also glowing.  That’s because there’s a 500w equivalent CFL in there.  Lightbulb the size of a football.  The cool part (no pun intended – yeah right) is that you can actually handle this bulb while it’s on without screaming like a little girl.  Show off to your friends who don’t know better.

Quick tour:  The bottom gray part is full of water (reservoir).  Full.  Of.  Water.  If you thought the Earth Box was heavy…

Let’s do the math.  It’s an 18 gallon bin with about 16.5 gallons of water in it.  At 8.34 pounds per gallon we have 137 pounds.  Now I see that number and like you (probably) I think “hell, I can lift 137 pound easy”.  And like most adult males I’m correct in that it’s not that hard to lift 137 pounds.

Of a solid.

One of two things will happen trying to lift a rubbermaid bin with 137 pounds of water in it.  1 – you really, really hurt yourself.  2 – you dump all the water out of the bin.  Or perhaps even 3 – both #1 and #2.

I’m not kidding, don’t pick up on this thing.  If you absolutely do have to move it, grab the sides with both hands at the corners, squat down, lean back and drag it using a combination of your weight and legs.  Go slow, go smart, and keep in mind that the water is going to slosh.  The lid?  Ornamental in the face of a wave with 137 pounds of water behind it.  It can and will pop off if you slosh enough.

This is one thing I was not required to learn the hard way, btw.

Next up (going up) is the thin black stripe around the middle.  That’s the lid to the reservoir.  It’s painted black with Krylon paint to block the light from getting to the water.  Light + water = slimey yuckiness.  Light + water + hydroponic nutrients = the most vile slime mold you can imagine.  Light is great for plants, bad for water and roots.

Above that is the “enclosure” assembly.  The gray and blue are connected and hollow all the way to the top, giving us a lot of vertical room to grow in.  Inside it hangs our light.  Up top we’ve got a thermometer with a remote probe to the inside, a pair of PC fans (powered by a hotwired PS seen at the left) and the hooks that hold the chain that supports the light.  On the floor in front is the power strip everything runs off.

Let’s look at the parts in greater detail:

Here we have the reservoir.  And my foot again.  ‘Cause I’m a rebel.  (Note, this would be supremely stupid if I were inclined to grow things I ought not be growing.  Not that the cops have a major foot database or anything, but you just don’t do anything “The Man” can use against you.)

Inside we can see the two air stones that aerate the water.  You’ll notice that there’s already a hole in the handle of this bin (compare top and bottom).  I just drilled another one for my second airline.  Since my pump has dual outlets, I ran separate air lines to each stone.  You could just as easily split the line with a T connector inside the tank.

Oh, and always use check valves.  They prevent the water from being able to flow back up the hose and into your pump (which ruins it) when it’s not running.

That’s what it looks like when it’s running.  If you don’t get a vigorous “boiling water” effect, you need a more powerful pump and/or bigger/more air stones.

Here’s the top.  Spray painted black because let’s be honest – no rubbermaid bin is light-tight off the shelf.  (If you don’t believe me, put a bulb in one and shut the room lights off.  Or better, yet, put a 500+w in there and admire the glow.)  Measure out and cut holes in the top (trusty thumb-stabber to the rescue – no thumbs or anything else stabbed in this venture) and pop in your net pots.  You don’t need big ones, it’s not about how much medium you can hold.

You can see I’m not actually growing anything hydroponically here – I’ve still got seedlings in Jiffy starters.  I just put them on top so I can assemble and run everything until the seedlings are big enough to move into their new home below.  (Most are going outside, actually.)

Seedlings are, starting in the right tray, two basil plants on the far right side.  One for hydro, one for outside.  Next row to the left is lettuce and collard greens (two lettuce, collard at the bottom, all for hydro), 3rd row is garlic that doesn’t seem to want to grow, 2 spinach (for hydro), and the Mystery Seed.  Last row is onions, 2 per starter, for outside.

The other tray has 3 more collard greens for outside, spinach at the bottom, and then a 3 starter row with 2 carrots each for outside.  The last two starters are the pepper plant (the one I thought might be my cherry tomato, and an actual cherry tomato.  The white thing is a paper towel growing some left over lettuce seedlings to be eaten as sprouts.  I had more germinate than I needed, they wouldn’t take the heat outside, and it seemed a shame to waste them entirely.  (I had one already.  Tiny sprout an inch long, more flavor than anything that size has any right to have.  Lovely.)

Here’s another shot of the whole rig, except this time with no flash.  You can really see the glow I was talking about.  I can’t stress this enough.  Rubbermaids are NOT LIGHT TIGHT.  If you don’t paint them you’ll grow nasty stuff.  In fact, you can see the glow inside the reservoir (cool effect with the bubbles, but not what you want).  That’s coming through the net pots, which as you can see in the previous picture weren’t filled up because they’re waiting for the seedlings to get big enough to transplant.  Since taking this I’ve put a thick sheet of cardboard between the seedling trays and the lid.  It’s now appropriately light-tight.

Note that the computer fans up top are not the LED variety that light up.  That’s a bit of light leaking out the top, but it’s about as bright as a normal LED fan, so I’m not going to worry about building a light trap for that.  (I had ideas but tossed them since they weren’t needed.)

Top view.  Here you can see the fans and the thermometer.  The wiring is properly spliced (use solder, it’s worth the effort to be safe), wrapped in electrical tape, and so forth so that the two fans are run off a single connector.  The duct tape (don’t DIY without it) is just there to keep the wires from getting pulled.  If you look closely you can see small holes on the outsides of the fans.  Through these come the chains that hold the light fixture up, and they hook on the little golden hooks sticking up.  This means I can easily raise or lower the light.

You can see it more clearly here.

I like this shot because it shows a lot more than it seems to at first…

The white wire is the remote sensor for the thermometer, it goes into the cut-out handle, and is duct taped to the inside – the dark square right under the Sterilite sticker is the tape.  Also, if you look up to the demonstration of the bubbling you can see the tops of the handles there – where the air lines go through.  On this part I’ve sliced them off to make a nice long, narrow opening.  Those fans blowing out the top mean air has to come in from somewhere – this is where it gets in.

The blue bin’s handle makes a convenient place to store the excess wiring.

This is just a spare computer power supply (PS) I had laying around.  As you can see from the tangle of wires on the right, I’ve butchered it pretty soundly.  This was done to make it so that it would come on without being attached to a computer.  This is not something you should DIY unless you’re reasonably familiar with electronics.  You can and will zap yourself pretty badly if you don’t know what you’re doing (and it could potentially kill you).  This is an ugly looking thing, but it’s safe as long as you don’t let kids play with it.

As you can see I’ve labeled this PS as “OK, Crappy”.  That’s because it is.  It works, but for running a computer it sucks the big one.  That’s why it’s doing this instead of running a computer.

If you want to do something like this, first read this How to Convert a Computer ATX Power Supply…

If you don’t understand that, please don’t mess with a power supply.  Those who understand all that will see I didn’t follow those instructions – I skipped a lot of steps and basically just “hotwired” my power supply because I didn’t need the versatility.  Mine’s kind of a “one trick pony” but that’s all I needed.

Here you can see the wiring running up the back to the fan connector.  This means I can easily reach back and disconnect the fans (thereby the top) from the power supply to move it around.

And speaking of the fans, here’s how I mounted them.  I took a sheet of paper, pushed it down on the back of a fan, and then rubbed it with my fingers (which left darker marks on the paper in the shape of the fan – my hands weren’t terribly clean).  I then cut out the inside shape of the fan from the paper, and used that pattern to mark the bin with a pen.  Cut out those holes, drilled the holes to screw it in, and used normal fan screws (they should come with a set of four).  Just drill the holes smaller than you think you need.

Also, the white wire isn’t needed – it’s a speed controller thing that doesn’t work when you’re running it straight off the PS.  Mine are just cut off.

This was a tough shot to get.  You’re looking down into the bin through a fan.  You can see the chain going down to one side of the light fixture.  The “white” is the light around the edges of the fixture.  Not a very great picture, I realize, but I like it.

This is a picture straight up the top part.  You can see the light fixture pretty much takes up the whole thing.  It’s nothing more than a 18×24 sheet of aluminum screwed into a thin bit of wood about 17×5.  I just bent the sides by pushing the wood down on the middle and lifting the edges.  Once I had the shape I wanted, I drilled holes and screwed it to the wood (wood on the back or “top”).  I then hung the light with a couple bent pieces of a wire hanger.  They go through holes drilled all the way through, and then are bent on top to keep them from coming out.

Not elegant or even ideal, but it works.  I was impatient.  BTW, this fixture cost all of about $14.  Ten for the metal and 3.50 for the socket with 15′ cord.

You can see the temp probe here.  It reads hot due to proximity with the light, but I’d rather that than have the plants hotter than I think they are.

That’s where the power cord for the light goes.  You can also feed it up between the gray and blue bins, but I had trouble with it messing with the fixture’s balance that way, which is unfortunately hard to correct with this design.  When the light is higher up, this will be a better option.

Here’s the finished product again.

The reason the half gray bin and blue bin assembly isn’t actually glued together is simple.  When I first started kicking around the idea of using an inverted bin as a mini-enclosure I realized that with my low-level leafy vegetables (lettuce) I would probably have trouble getting the top on without trapping leaves between it and the top of the tank.

But this way I can remove the gray from the blue, then put the gray one on top alone, making sure all the leaves are nicely contained within.  Then the blue – with light – can be lowered on top of that and not trap/crush any foliage.

If I left anything out or you have an questions about how I did something, let me know.

Unfortunately, I was just too excited to get this done to properly document the fabrication process.


2 Responses to “My Quick and Dirty DIY DWC”

  1. LotSmonidot Says:

    Fantastic website – hope to visit again=D

  2. Alex Says:

    Good info, I’d just like to add one thing. If you’re using a 500W equivalent CFL (im assuming 125w or 150w bulb) you should get yourself a ceramic socket. It would be safer.

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