Introduction: Hydroponic Food Factory

About: Software engineer, using electronics and micro controllers as a hobby to keep me sane!

Build your own outdoor hydroponic system to grow Potatoes, Strawberries, Lettuce and Celery!

I have been interested in hydroponics from a very young age when a relative gave me a "grow light".
Being young, I didn't realise hydroponics meant growing without dirt, but that didn't stop me trying to grow plants under my parents stairs!

Ever since seeing my strawberries growing under that purple fluorescent glow, I was mesmerised by the idea of growing plants in different ways.
When I learnt that hydroponics was about growing without dirt (and not artificial lights!), I was hooked even more.

I have researched for years, and recently took the plunge growing a small hydroponic chilli plant, that shot up above it's dirt bound siblings. That was it for me, I wanted more, and I wanted bigger!

So here is how I built my new hydroponic garden, I hope to inspire others to jump in, it is a great hobby!

Step 1: The Green Side of Life

Hydroponics is not only an enjoyable hobby, it is also a green one.

Hydroponics use as little as 10% of the water needed for plants grown in dirt , and results in higher yields due to the plants always having the necessary nutrients available to them when they need it.

Being a closed system, it also means that fertiliser is kept out of the water table, which is great for the environment.

An added benefit is that there is a less chance for weeds and dirt bound insects to attack your plants, so there is less of a need for chemical poisons.

Going further
Keeping with the green spirit, this instructable uses recycled materials where possible, and uses a low power pump, to keep electricity use low.

From using old PVC pipes, an old wooden baby's crib and other miscellaneous junk, not only is the cost kept down, but so is the waste.

As for power, the only thing needed is a water pump.
A small submersible pond pump kept the power usage down to a small 18 watts, which is about that of a CFL and less then a third of an Aerogarden!

When it comes to lights, it is hard to beat the Sun!
Free, effective and carbon neutral, it provides the exact spectrum that plants have evolved to use.


By growing food in my garden, it is a little bit less food I need to buy, a little less food that has been shipped across country, by trucks.
No packaging, and no transport makes this food the greenest in my kitchen.

Step 2: What You Need

This won't be everything, but it the majority of what you need to build a hydroponic garden like this one.

PVC Pipe
I had one long piece from a friend, and I bought two precut pieces from the hardware store.

End caps
A cheap way to seal off PVC pipes (who would have guessed!)

This is where our water starts and ends. You want this to have a decent capacity, so the pump won't run dry.

Submersible pump
I bought a small 18w pond pump.
It is important that you look for one with a plastic impeller, as metal ones will most likely corrode from the dissolved salts (nutrients) in the water.

Plastic cups
These will be the new home for your plants.
Buy more then you need, as you will probably have to destroy a couple for measurement purposes.
Also, don't get clear ones, clear cups will let light in, and encourage algae growth.

Silicon sealant
If I was to do this over again, I would have opted for grommets, but silicon does a decent job, and it is handy if you have any small leaks you need to plug!

Garden Hose
A friend insisted I use a bit of his expensive hose, as it will bend better with less kinks.
He was right, but in the end it wasn't enough for everything, so I also bought a cheap hose for extra length where I needed it.

As a bonus though, I got some hose fittings, which I was able to turn into a handy float valve! Read the instructable for it here: Hydroponics Float valve

Only needed if you need to cut up a long piece of pipe like I did (and the wooden frame).
Looking back, I should have left it out of the picture, it wasn't as important as I was thinking.

Step 3: The Concept

In hydroponics, it is all about getting the nutrient rich water to your plant's roots, while making sure there is enough oxygen in the water so they don't drown.

Here we are building an NFT (Nutrient film technique) system using PVC pipes.

The basic idea is that we want a small, but constant flow of water that the plant's roots can sit in.
The water contains all the nutrients the plants want, and the constant flow means there is plenty of oxygen in the water.

The plants need something to support them though, seeing we won't have dirt to hold them up, this is where hydroponic mediums come in.
I have three that I have been working with, perlite, vermiculite and expanded clay balls.

These will give the plants support, and a small buffer to hold water.

Now, we don't want these being washed away, so we will be putting them in little plastic cups, and let the roots grow out small holes into the stream of water.

Step 4: The Hole Template

Now that we know what we want to achieve, lets start building!

Make a template
Get a plastic cup, and line it up to the end of one of your PVC pipes.
Choose how deep you want the cup to go.

Don't have it sitting in the water level, leave it a little above the bottom, don't worry, the roots know how to find water.

Mark the point onto the cup.
Cut the cup along the line you marked.

Get a scrap of cardboard, and draw a line around the cut off cup (the top part).
Cut out the hole, and test it with a new cup, to make sure it fits, and is at the height you want.

Work out how many cups you want in your pipe (I picked 10 for two pipes, and 3 for the other two).

As my pipes were 1 metre long (~3 feet), I centred my templates around a 10 centimetre (4 inches), and made a small whole on each side of the big hole.

The two small wholes give you an easy way to make sure each cup is spaced evenly apart from each other.

Step 5: Making the Cut

Start by putting the end caps on your pipe.
This will give you a safe area to cut in.

Get a piece of tape, and run it along the pipe, making a straight line.
It doesn't need to be perfect, but you will need the cups to line up for the most part.

Now, move the template along this line, making a mark in the two holes.
When you move to the second spot, line the first hole up with the mark left by the template.
Do this the whole way along.

When you are done, remove the tape, and go back and draw in the circles.
I used a black CD marker, but anything that will draw on PVC pipes will do.

Now, get your drill bit ready!
Drill small holes to mark out the circle.
The closer they are, they easier the next step is.

Now push your drill bit, slowly from hole to hole, just connect the dots until the middle drops out.

The result is a bit rough, but put a cup in, and figure out what needs cleaning up.

Get your dremmel tool, with a grinding head and clean up the hole until the cup fits as you wanted it too.
This is messy, don't breath in while you do it, protect your eyes, and expect to look a bit like a snowman by the end of it all!

Do this for all your pipe.

My two strawberry pipes, I did 10 cups in each.
The other two, I wanted more spacing (for the lettuce for example), so I put only 3 cups in, equally spaced.

Step 6: Support Frame

We need a frame to support our pipes, nothing fancy, it doesn't even have to be all that strong.

Not everyone will find the same unwanted junk as I did, so be creative, look at what is around, and imagine what you could create.

I found an old discarded baby's crib, it was structurally sound, but I wouldn't use it for a baby, it just didn't look healthy enough for that.
So, instead of being discarded, it has now found a new home, doing something useful!

Building it
I put the crib in my greenhouse, and found that half of it fit in perfectly, right before the hinge point.
So I unscrewed the hinge, removed the section from the hinge to the front, and then rejoined the front.
(I also go rid of the entire top section)

Now, this doesn't support itself, so I took the metal locking strips, bent them, and turned them into a support.

I only had the two piece of metal, so the front and back only had one support each.
This did make it a bit wobbly, and later on caused some issues.
I'll show you how I fixed that in a later step.

Step 7: Support for the Pipes

To support the pipes, I decided on using a plastic mesh (plastic chicken wire?) I had left over from a different project.
I ran it from the top frame of my greenhouse (cover off), down to the front, making sure it was at a decent angle to keep the pipes going on an approximate 45 degree angle.

Support the mesh by tying it to the greenhouse, and frame with twist ties.
I had a large roll of the stuff (useful for training plants too), and used it liberally to hold the mesh down.

When I knew how far to take the front, I cut the frame as needed.

You will also need to cut out the middle poles so you can get your hand in, and work with the bucket if needed.

Add the pipes
Add your pipes to the mesh, and tie them into place with more twist tie wire.

Step 8: Drill the End Caps

Make another template on cardboard, based around the hose.

You will want to cut a little smaller then the hose, we want the fit to be tight.
This is much the same as cutting the holes in the PVC, just aim for a tight fit, this will hold the hose in, and provide a bit of a seal.

Step 9: Lock the Hose In

A tight fit won't be enough to ensure the hose stays put, and the last thing you want is water pumped all over the ground, dead plants and a burnt out pump!

Get some stiff wire, such as a coat hanger, cut a small piece.
Drill a hold right through the end of the hose, push the hose into the end cap, then lock it in with the wire.
Bend the wire a bit so it doesn't just slide out of the hose.

Before you seal the joint, put the end cap on the pipe, and measure the length of hose needed to go to the next pipe down.

Use some waterproof silicon sealant on both sides to finish the job.
Let the silicon set overnight.

Step 10: Cap the Ends

Push the caps onto the pipe, and mark how far it goes.

You only want to glue in one half of the cap pair at a time, as the hose will push outwards and pop the cap off otherwise.

Line the caps up so the drain hose is at the bottom, and the other end goes to the top of the next pipe.
This way, when the water flows, it will splash around more, dissolving more oxygen into the water, which is important for the plant's roots.

The blue stuff I'm using is a plumber's cement.
A friend gave it to me, it is about a decade out of date, but we aren't doing anything too important here, so it does the job just fine.

You want to paint it on liberally on both the pipe, and the inside of the end cap.

Push the end cap on, and make sure you have the hose lined up right, hold the end cap firm for about 5 minutes while it sets.

You need to give it a day to fully dry properly before you complete the other join.

Step 11: Overflow!

I powered up the pump, and very quickly there was an overflow.

There were a few steps to fixing this properly:

1. Turned the pump down to a lower flow rate.
There was a small dial on the front of the pump for this.

2. Add more support to the front
I used a piece of square guttering that I found laying around.
At first I tried to bend it, but it ws way to strong, so instead I held it in place, and put screws there to hold it in place.
This worked really well, and was a simple fix.

3. Raise each pipe until they flow from one to the other better.
I moved everything up a lot more then I first planned, but this really helped the water flow from one pipe to the next.

These steps helped a lot, but apparently, my small pump (on low!) wasn't small enough, and I actually needed to kink the hose a little to reduce the flow further.

Step 12: Prepare the Cups

So, our little plants will need somewhere to live, so get your cheap plastic cups ready.

You just need a small drill bit, and some patience.

I would recommend lining up all the cups, and making a drill pattern that you can repeat per cup.
That way you know they all have enough holes, and you can drill each cup without thinking.

I drilled the base (cup upside down), and then around the sides on little plastic marks around the cup.

Now, left like this, perlite and vermiculite will simply wash away through those holes, so you should put a small layer of clay balls to prevent that.

The clay balls have a fine orange dust over them, so you will need to wash them off.
I found it easiest to put them in the drilled cups, and lower the cup into a bucket of water.

Step 13: Planting Time!

I wanted to have plants in my setup quickly, and I couldn't wait for seeds, so I liberated some dirt based seedlings!

Before you work on the plants, you will need to get your planting mediums ready.

I mixed perlite and vermiculite in a 50/50 mix, to provide good aeration and water retention.
If you aren't doing the potatoes later, you don't need anywhere near as much as I have there (a 12 litre bucket).

If you have the time, you will get best results by growing from seeds, but if you are impatient like me, then buy some seedlings and follow on.

Pop your plant out of it's tray, and gently remove as much dirt with your fingers as you can, all the while trying not to disturb the roots too much. (picture 3)

With a bucket of plain water, dip the plant roots in and gently wash the dirt away.
You won't get it all, but do your best. (picture 4)
If the roots are tangled (like with my celery), you will need to slowly pull the plants apart, do your best being careful with the roots. (picture 5)

Now, grab your cup with already washed clay balls at the bottom, hold your plant in there, and pour in your medium mix. (picture 6)

When you are done, you should have a plant that can hold itself up (picture 7), if not, pack it down a little more.

You should give the cup (with plant in it) a quick dunk in the water bucket, and then move it to it's new home in the PVC pipe (picture 8)

Step 14: But the Roots Are Too Big!

So, you get to the strawberries and wonder how you are going to fit that massive root ball into the small plastic cup, right?

Before you even wash off the water, get some clean scissors, clean them with some rubbing alcohol and carefully cut through the dirt.
Do this as little as possible, as it will stress the plant.

It is better to make one big cut, then to make many small cuts.

With the root ball being so big, I also found I needed a little pressure from the garden hose to wash the dirt off.

Once you have done that, the plant should fit nicely into the cup.

The strawberries were also a bit more expensive then I had planned, so I have planted them in alternate cups, leaving the other spaces spare.
I have two ideas for this, either leave them spare (the plants are quite big anyway), or wait until these plants send out runners, and I will get the other 10 plants for free! (also they will be free of dirt!)

Step 15: Water & Potato Bins

The water and potato bins need the exact same modifications, so just do the following twice.

Drill a hole big enough for the hose to squeeze through (you should have some practice in this by now!)

You want the hole as low as possible, so you can drain out as much water as you can.

Hook the metal wire, and silicon seal the joint just like you did for the end caps.

The potato bin will simply drain back into the small reservoir, while the water bin will need to be hooked up to a float valve.

You can either buy a side entry float valve, or even better, just follow my instructable on how to make a very cheap one here: Hydroponics Float Valve

I'll go into more depth on mounting the float valve later

Step 16: Drip Ring

The potatoes shouldn't be in a stream of water, but they do need a steady supply of water and nutrients.

This is where a drip ring comes in.

You will need two T pieces that fit your garden hose.
Cut a length of hose that will make a nice sized circle, and join it with the T piece.

Use a pin, and make a lot of little holes around the hose.

On the pump line, cut it above the height of the potato bin, and rejoin with a T piece.
Join the drip ring to the pump line with a piece of hose long enough that the ring can reach the bottom of the bin.

Step 17: Hydroponic Potatoes!

Hydroponics isn't just for above ground plants, with a bit of creativity (and a good hydroponics book!!), you can find ways to plant pretty much anything without dirt.

Potatoes can be started from any potato with eyes.
You can even start from a small slice of a potato, as long as it has an eye to start a root from.

Ideally you will want to get a seed potato from your local nursery, as it will be disease free and healthy.
I was a bit impatient however, and just grabbed a potato from the cupboard!

The plan here, is to plant the potato at the bottom of the bin, and as it grows, add more medium around the plant. (look at the second, badly drawn picture!)
This will give us more potatoes, and let us grow vertically.

One very important note here, don't let any potatoes grow uncovered. Uncovered potatoes will go green, and green potatoes are poisonous!!

Start by lining the bottom of the bin with some clay balls, this will allow the water to drain better.

Place the potato in the centre and cover with a 50/50 perlite & vermiculite mix and put in the drip ring.

Now, being so deep down in the bin, it would help if we could direct some more light into the area.

One of the best ways to reflect the light that plants like, is to use a reflective material called Mylar.

Mylar in rolls for hydroponics is a bit expensive, thankfully it isn't just for hydroponics, you will find it on shiny balloons, and chip packets!

Having a big multi-pack available, I cut it open, and stuck it into place.
So shiny!!

Step 18: Add the Float Valve

Fix the float valve to the water bucket so the float sits in the water, and the water flows into the bucket.

My greenhouse came with two metal meshes to act as a floor, or something, so I tied one to the bucket, and tied the float to it.

Attach the hose to the float, and you are done with construction!

One last thing you want to be sure of, is where your power cord is.
Keep it up high, and off the ground.
One overflow and you could be electrocuted, don't mess around with electricity!

Step 19: Maintenance

Some of your plants won't take to the new system right away, for the first week or so, you will need to add a little bit of water from above while the roots find there way to the flowing water.

My Strawberries did this to me the second day, they were wilted and not happy.
A small dose of nutrient water from above, and the next day they were standing up happy!


I have a small box of nutrients from a previous project, so I started with this.
In future I'm planning on buying in bulk for the longer term.

With a powder based nutrient mix, you will generally have two parts.
Follow the instructions on the box, and fill your small reservoir and your bigger tank.

My small bucket is 20 litres, and the bin is 60 litres.

The box has instructions for 100 litres, so it is simply 80% of the instructions, mixed straight into the water.

Lettuce & Celery

While the strawberries will go on happily, I will have to harvest the lettuce & celery at some point.
I'm planning on replacing them with seeds, as lettuce will come down to only a few cents each, instead of the $1~$2 I would pay at the shops!

Step 20: Update 1 - Flush

It has been a while, so I thought I should make an update on maintaining the system.

I wanted to address the questions about nutrients properly, so I thought it would be a good time to flush my reservoir, and make up some fresh nutrients.


About once a month, it is a good idea to start fresh with the water, as the plants would have taken most of what they want by now, and the nutrient level will be a bit low.

Start by disconnecting the bigger water tank (I just put a normal hose fitting onto it in the closed position to stop the flow).

Turn off your pump, and disconnect the pump hose.

Attach a spare hose piece and send it out to your grass (or dirt plants, there are still good nutrients they can use in here!).
Turn your pump on, and let it empty your reservoir.
Don't let the tank run dry, it can damage it, you might need to tip out the last litre or so of water.

Give your reservoir a clean if it needs it (some of the orange dust still on the clay balls probably washed away by now).

Hook your hose back up, and make up your nutrients (next step)

Step 21: Update 2 - Nutrients

Some comments below made me realise I was a bit lacking on the nutrients section, so I thought I should clear some things up.

Hydroponics needs special nutrients, normal fertilisers won't work.

In dirt, there are a lot of microbes, that break down things such as manure to produce the elements plants need.
In hydroponics though, there are no microbes, so we need to give the plants the elements they need directly, no middlemen (or is that middle-microbes?).

Hydroponics nutrients can come in different mixes for different stages of plant growth.
If you really want to get into hydroponics seriously, you will eventually use different mixes for the veggative and flowering stages. These will be more fine tuned to what your plants need, but they need more attention to detail, so you switch them at the right times for best results.

Personally I just want this as a hobby, not a full time job, so I am going for a general all round mix, which will give good results, but probably not the absolute best results.

Make sure you flush your reservoir as per the previous step.

Now mix your nutrients as per the instructions.

My box gives instructions for 100 litres, but I only wanted to fill my 20 litre bucket (not the 60 litre tank).

So, I divided the instructions by 5, and then mixed it into a 2 litre bottle (it was easier to shake!)

After it is well mixed up, pour it into your reservoir and then top it up with fresh water.

Turn your pump back on and your plants will be happy :)

Step 22: Update 3 - Flooded Potatoes

A week or so after I set my system up, it rained, hard.

It made me realise a small flaw in my design, any rain that falls on the potatoes floods it with fresh water, which then drains back into the reservoir, overflowing it.

A simple fix was to get a clear garbage bag, cut it open, and attach it to the greenhouse, hanging over the potatoes.

I even got to test this 1/2 an hour after I finished it, as it started to rain!

Step 23: Update 4 - Hose Blockages

My hoses haven't blocked yet, but a couple of people noted that when the roots really take off, I could be in for some trouble.

So I found some old fly screen mesh, cut a few squares out of it, and pushed it into the ends, covering the hoses.

Hopefully it will be enough!

Step 24: Update 5 - Potato Status

I was asked in the comments how my potato was going, and I was curious myself, as nothing seemed to be happening.

So I started digging it back up, expecting disappointment, but the potato seemed to be logged in pretty strongly.

I carefully got it out, and I think the picture speaks for itself!

Now I just have to be patient and wait for a green shoot!!

Step 25: Update 6 - Dirt Vs Hydro

Give a general description of the Step it might be interesting to see the difference in growth between dirt and hydroponics.

Luckily, when I had leftover lettuce and celery plants, my wife planted them in dirt.

The plants all came from the same punnet, the only difference is one is hydroponic, and the other dirt.

Have a look at the pictures to see the difference!

Step 26: Update 7 - Is It Natural?

I had a question in the comments which I thought was important enough that I should make a step just for it.

The question was: (from arirang777)
"People usually complain about using fertilizer because it is not "natural" or organic, etc. but here we are feeding the plants with pure chemicals diluted in water. I am having this crazy idea of veggies on stereroids. Can we still call it "natural"?"

Natural & Organic are misleading terms.
Plants only take in basic nutrients, such as nitrogen, Potassium, Calcium etc.
Have a look here:

If you have ever done a science class, you will notice they are all basic elements from the periodic table.
There is no such thing as inorganic nitrogen, it either is nitrogen, or it isn't!

When you feed dirt plants things such as manure, they can't eat it. They rely on tiny micro-organisms to break it down to the base forms they need.

All we are doing here is skipping the manure & micro-organisms and giving them what they need directly.

The reasons the plants grow so well, is not because we are drugging them, but because we are giving them a massive buffet of all the foods they want!

I'll add a picture from the side of the box later, showing the composition of the nutrient mix, and how each part is simple an element from the periodic table.

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