ebb & flow: a recurrent or rhythmical pattern of coming and going or decline and regrowth.

What is it?

This set of instructions will give you a basic idea of how I put my ebb and flow hydroponics system together and how you can create your own. I wasn't thinking of putting these instructions online initially, so I apologize for a lack of pictures of a few of the smaller details. However, I'm here to help if you have any questions.

As an experiment, I planted two of the same types of a few plants in soil the same time as in this system. The growth rate of the plants in my system is almost double that of the plants in soil. Yay for happy feelings of self-accomplishment!

Why did I do it?

I am fortunate enough to love plants, understand a little about technology and building things, and have a balcony that gets nice, full sun. Living in New York City, gardening is almost impossible so I had to make due. I created an extremely basic, yet customized design that would fit on part of my balcony. This design was made exclusively to be used outside with natural light, although you could easily mount lights above it indoors.

What am I growing in the system?

Being my first time with this setup, I wanted to grow a few different "types" of plants, but plants similar enough in their watering and nutritional needs that I wouldn't have to worry about that side of things.

Cherry Tomato
Cucumber
Snap Peas
Brussel Sprouts
Thyme
Oregano
Basil
Spearmint
Summer Squash
Watermelon
Pumpkin
Mustard Greens
Sweet Peppers

What materials do I need?

All of the supplies I procured at my local Home Depot, except the Hydroton clay pebbles and B-52 vitamin solution, which I got from Amazon.

1" PVC piping and joints (Ts, corners, etc) <-- more on this in the upcoming steps
1 x 1" threaded T joint
1" to 3/4" threaded adapter
PVC glue
Dark paint (1 quart is enough)
Several feet of heavy duty velcro
Screen patch kit(s) or other mesh material that allows water to pass through it
14 x 2 litre soda bottles (exact number varies by your design)
Epoxy or other thick, strong glue (I used Weld-On #16 Thickened Acrylic Glue)
Flexible 3/4" tubing (get 4 ft so you have room to cut and place it where you need it)
6-8 liters Hydroton clay pebble growing medium or growing medium of your choice (exact amount varies by your design)
Outdoor water feature pump or strong fish tank pump (100-150 gph is fine)
Aeration stone, tubing, and air pump (typical stuff you'd put in a large fish tank)
Rubbermaid container
Timer (make sure it allows you to set smaller increments of 15 minutes or so)
Vitamin solution (I used B-52)
Rope, twine, or other method of support for your taller plants
Plants (duh)

Anything else to remember?

Think ahead and feel free to improvise, but keep a few basic things in mind:

Leave enough room between planting pods for your plants to grow and expand.
Make sure you can easily refill your reservoir and check the water level.
Put the system in a place where it will receive lots of light. Since you're essentially supercharging what's happening "below", you have to make sure what's going on "above" can match the growth needs or your roots will rot.
The taller, more heavier plants (and those that climb) will probably benefit from some added support since there's no soil to anchor them in the ground. While the clay pebbles are sturdy, there's still not as strong as if the plants were rooted in the ground.
Your friends are going to ask lots of questions about how you did it! Take pictures be ready to show everyone.

If I could do it all again...

... I would make use of 3D printing. There are several issues I ran into and solved that would have been made easier if I used 3D printed parts. I'll call out these areas for improvement specifically as they arise in the steps.

Enjoy!

Step 1: Create Your Design and Glue the Piping Together

I recommend drawing the design out first on a piece of paper. This way you can count the number of T-joints, corner joints, length of PVC piping to buy, number of 2-liter bottles to save, etc. At Home Depot, next to the PVC piping, they had the handy little PVC cutter for a few bucks. I would have used a chop saw if I had one (or had a garage to put one in).

Cut your 1" PVC tubing to length. Lay it out with your corner joints and upward-facing T-joints in place before you start glueing to avoid mistakes. The tops of the upside-down 2-liter soda bottles will connect to the T-joints.
- At one end, one of the upward-facing T-joints will become your overflow line. More on this later, but make sure you don't put a 2-liter bottle in this one.
- Make sure that at some point in your design, you install the threaded T-joint. This has to be at least parallel to the ground or facing downward so that the water will drain back out of the system when not being pumped in.
Once you're sure everything fits and is cut to length, glue it all together with the PVC glue.

Step 2: Prepare the Soda Bottles

Chug all that soda or raid a recycling bin. I used 14 2-liter bottles in my system.

Peel off the labels.
Using a cutting tool of some sort (I used a utility knife but a chop saw would be more than effective) cut the bottoms off of the bottles. You want to save most of the widest area of the bottles for the plants to grow in.
Using the same tool I bought to cut the PVC pipes, I cut the threading off (below the ring) since it doesn't fit inside the 1" PVC piping.
To prevent algae growth and help the roots grow, paint or spray the bottles a dark color. It doesn't have to be perfect, but you want as little light reaching the water as possible.

If I could do this again, I'd create a 3D printed "soda bottle thread --> 1" PVC pipe" adapter so that I wouldn't have to cut the threads off of the bottles. This would give more stability at the point of contact where the bottles meet the piping. Not having done this, I don't know if it would have leaked, but I would have used plumber's tape when screwing in the bottles. This would also have allowed me to unscrew individual plants without breaking any glue seals (in the case of troubleshooting clogged pipes).

Step 3: Attach the Bottles to the PVC Piping

Using a light coat of the PVC glue in the top of each T-joint, glue the bottles into the piping.
Once the glue dries, take your epoxy or acrylic (heavy duty) glue and using a glove-covered finger, fill in all of the space in the joint where the bottles meet the piping. These bottles have to withstand bumps, wind, heavy plants, etc.
Once the above step dries, cut the screen patch kits into a hexagonal shape and secure them into the bottom of the bottles on the inside using your glue of choice (I used my acrylic glue again). This ensures that none of the growing material falls into the piping and will help prevent clogs.

Editor's Note: The roots of some of at least one of my plants (cucumbers) have grown through this mesh and is starting to slow the overflow process. You might want to find a different material with smaller mesh to prevent the roots from entering the piping (make sure water can still pass through easily!).

Step 4: Give It Legs and Connect the Prepared Reservoir

Here is where my pictures get a little few and far between (my apologies). You're going to want to give your system some strong legs to support the weight of the water, plants, and wind. I used some extra PVC piping and some screws/nuts I had laying around to give my system something to stand on. You have to make sure that your legs are tall enough so that the threaded fill nipple is higher than the hole you put in your reservoir for the water tubing. You want gravity to be able to pull all the water back out of the system when the pump is off.

Make your legs/stands. Cross brace everywhere you can.
Using a Dremel tool, I sanded the tops of the legs into half-circles so that the PVC pipe from the system can rest on the legs with more surface contact (glue the legs in place too).
- I found it easier to use velcro to keep the legs from buckling under themselves. Make sure you stretch it nice and tight to stand up against wind.
Drill a hole in the top of the side of your reservoir (I used a 20gal Rubbermaid container) for your flexible tubing to pass through. Connect one end to the threaded nipple and the other to your pump.
Drill another hole under one of the handles large enough for the pump's power cord and air tubing to pass through.
Get the aerator and air pump ready to go. You want to keep the water aerated, so put the air stone in along with the pump and pass the air tubing and power cord through the hole you made above in step 3.

If I could do this again, I'd 3D print "half moon --> 1" PVC pipe adapters so that the base fit more security onto the legs without the need for as much cross-bracing.

Step 5: Create the Overflow Pipe

This picture was taken long after the system was in place (which is why there are already plants growing), but it's to show you how the drain should be created.

The water in your system will keep being pumped higher and higher until it overflows... either over the edges of your bottles (which is BAD) or out of your overflow pipe.

Note -- I initially made the overflow point too high, which is why I have one tubed that is capped. Ignore that one.

Determine the level at which you want your water to rise to. This is going to be about 2-3 inches below the top of your bottles.
Cut more PVC piping to be at that level (be sure to take into account that you'll lose some length pushing the piping into the T-joint and subsequent corner joints).
Direct the water flow back into the reservoir. You're going to have to cut a hole in the reservoir lid for the piping to drop down into

If I could do this again, I'd try making the drain pipe much lower and just regulating the flow with a PVC ball valve.

Step 6: Add Your Plants!

This step assumes you've either started your own plants from seeds in some sort of soilless medium, or have already washed all of the soil off of the roots of your store-bought plants.

Since I used Hydroton clay pebbles, they are naturally a little dusty inside the bag. I dumped a bunch into a pot and took it inside to wash under the sink, removing as much dust and loose debris as I can before adding to the system.
Fill up a few inches of the bottles with your growing medium. Hold your plants in place and then add more clay pebbles until the plant roots are fully covered. Ensure that the plant is situated deep enough as if it was planted in soil.

Be sure to use the string/twine, etc to support any plants that need it. Give them somewhere to grow just like any traditional plant of the same type! Remember this version is going to grow super fast so be prepared to train your plants where you want them to go.

Step 7: Reap the Benefits and Enjoy

Make sure that you've covered up any area where light may hit the water. Algae is the last thing you want in your system and can actually damage the roots if it starts growing inside the system where the plants are loving life. I used electrical tape and wrapped the clear tubing between the pump and the fill nipple.

Timer Settings

Before the weather got hot during the day (above 75F during the day) I set the timer to turn on the pump for 15 minutes every 3 hours during from 10am-10pm. The other 12 hours (the cooler hours) the pump came on twice (every 6 hours).

After the weather reached about 80-85F during the day, I increased the watering frequency to be the same 24 hours/day (15 mins every 3 hours).

After it hit above 90F, I increased the daylight hours watering frequency to every 2 hours.

Helpful tips

Get some Grapefruit Seed Extract (liquid form) and add 7 drops per gallon when adding water. GSE is a natural algae killer, won't harm the plants in any way, and is fine for humans and animals to eat.
If your timer is outside, stick inside a freezer bag (or other large Ziploc bag) to keep the rain off of it.
Make sure your air pump is in a place where it will stay dry. The last thing you want in your air pump is water.

Keep an eye on the water level (make sure to add nutrients every time you add water) and enjoy the wonderful output from this system.