This instructable will show you how to build a simple ebb and flow hydroponic system. Out of the many different designs I have tried in the past, the ebb and flow has worked the best for me.

I have successfully grown smaller plants like lettuce and spinach as well as larger plants like zucchini and tomatoes with this system.

Sketchup Model
To make this design easier to understand, I have drawn up a Sketchup model and uploaded it to the 3D Warehouse. Here is the link "Ebb and Flow Hydroponic System Design"

Google Sketchup is absolutely free to download and use, so no worries if you don't have it already. It's awesome, and it makes CAD (computer aided design) easy.

With the Sketchup model, you can pan around to see how thing are put together better. Also, I needed to make the model just so you can see the entire system in one picture. The real version is inside of my solar greenhouse, which is kind of small. There is just no way for me to get far enough away to take the shot.

Pictures
One thing that I think is important to include when submitting hydroponic plans is pictures of the system in action. That way, the reader will know that the system works.

I'm putting mine here at the beginning where people are sure see them and get psyched about this project.

I have two cucumber plants and three tomato plants growing in these pictures. They still have a fair bit of growing to do actually. : )

My Website
If you're interested, my website is CerebralMeltdown.com. There, you can check out some of my CNC projects (a CNC is basically just a robot that will cut out designs with a wood router), Heliostat projects, (a Heliostat is a mirror that tracks the sun as it moves through the sky and reflects its light toward a single target) or just whatever else I happen to be working on.

Step 1: How Does It Work?

Here is a very quick overview of the ebb and flow hydroponic system.

An ebb and flow hydroponic system works by filling a container full of gravel with water and then letting it empty. (The water is, of course, mixed with nutrients.) A thin film will adhere to the gravel allowing the plant roots to gather nutrients even after the container has been drained.

Each act of filling and emptying is like a breath of fresh air for the roots. Filling the container removes the old air while emptying it draws in new air containing fresh oxygen. This is one reason why plants do so well in this type of hydroponic system, or, in fact, any system which creates a good supply of oxygen.

Picture 1
If you look at the first picture, you will see a pump at the bottom of the large container which stores the water between filling and draining (AKA "the reservoir"). A hose connects to this pump and splits off into the two containers which hold the gravel and the plants.

A timer turns the pump on several times throughout the day to fill the plant containers with water.

Picture 2
Holes are drilled into one end of the plant containers so that any overflow will drain back into the reservoir.
Note: The water must be able to drain out of these holes faster than the pump can pump it in.

Picture 3
A small drain hole is drilled into the bottom corner of each plant container over the reservoir. This lets the water drain out. It is important not to make this hole too large.
Note: The water must not drain out of this hole faster than the pump can pump it in.

Picture 4
One end of each plant container is placed higher than the other end. This ensures that the water flows toward the small drain hole.

Step 2: What You Will Need

To put together this hydroponic system, you will need...

Note: Items on the list appear in the same order in the pictures. (except for the wire, spray paint, water shield, and hydroponic solution.)

3/8" Pea Gravel 15-20$
The amount you will need depends on the size of the containers you use to hold the plants.

A few handfuls of larger sized gravel Free (Steal it from a driveway)

1/2" T-connector <1$ (Don't look in the garden hose section. It's too pricey. Try plumbing.)

Around 10' of an old garden hose Free (You can buy plastic tubing, but why not recycle)

Digital Timer 17$
Cheaper timers are available, but the shortest period of time you can set them for is 15 (or 30) minutes. The digital ones allow for more precise increments. To fill the plant containers, the pump only needs to be on for about 3 minutes.

Water Pump ~15$ and up depending on the gallons per hour.
Mine cost 25$ and pumps at 396 GPH. I bought a bigger sized one so that I can set up several systems if I want.

Two containers for the plants 5-10$
(Mine are 33" long, 14.5" wide, and 5.5" deep )
Notice in the pictures that they have been painted. This was done to keep algae from growing. I used regular house paint, which, of course, doesn't stick well. There is spray paint that you can buy that is designed for plastic. An even better option would be to buy opaque containers if you can.

Spray Paint ~5$ (Only necessary if your containers are transparent)

A large container for the water ~15$ (I'm guessing)
(Mine holds about 10 gallons. )
I'm using an old cooler that I had which is missing its lid. It has a handy little tap to drain the water out of, but they are flipping expensive to buy new, so don't worry about the tap if you can't find one. You can always drag out the container and empty it by hand.

Around 4' of wire Free (practically anyway)

Hydroponic solution 35$ and up depending on how much you buy.

Couple of Pieces of Plastic for the Water Shield Free (Scrounge something up)

Total Price ~110$

The price is probably a bit high because I did round up on a few things. I bought this stuff several years ago and can't remember the exact prices, so you might be able to shave off a few dollar because of it.

Also, you can run multiple systems with the timer and water pump, so you can double (or even triple) the size without doubling the price.

Finally, there is also the possibility that you might already have some of this stuff lying around or can find it on sale.

Step 3: Arranging the Containers

This step is pretty straight forward. All you need to do is set your plant containers on top of some cinder blocks (or anything really) with one end over top of the reservoir.

Picture 2
One end of the plant containers should hang over top of the water reservoir so that the water can drain back into it. The opposite end should be raised slightly so the water will flow downhill towards the small drain hole.

Picture 3
I should mention that the plant containers probably shouldn't be as far above the water reservoir as they are is in the Sketchup model. There is only a small gap between the two in my real life version.

You want to make sure there is enough space between the plant containers and the water reservoir so that you can easily pull it out if need be.

Step 4: Adding a Water Shield

Here you can see that I have attached a piece of plastic siding below the overflow holes. This was done to keep the water from flowing underneath of the plastic container and missing the water reservoir.

The plastic is held on with hot glue. You can see from the picture that I made a mess of it. I didn't think to do this until after I put in the pea gravel, and it was hard to get the containers far enough apart for the hot glue gun to fit in between.

You can also see why I recommended buying the special spray paint for plastic instead of just using house paint. It is starting to peel off. Of course, it has been on there for almost four years now, so it does last for awhile.

You might be able to skip this step if you angle the containers downward more than I did. I probably didn't think this part through enough, but it works. : )

Try experimenting to see what works best.

Step 5: Drilling and Covering the Drain Holes

Picture 1
The first thing you need to do at this step is to drill a small drain hole in the corner of the plant container. This one is 1/4" in diameter. You probably shouldn't make it any bigger because you don't want the water to drain out faster than the pump can pump it in.

The only reason to make this hole smaller would be if you were going to set up multiple plant containers, all filled with the same pump. I have only tried this with two plant containers myself, but I think that the quarter inch hole would work with four or maybe even six containers.

It's something that would take some experimenting to be certain.

Picture 2
The next thing you need to do is to drill the overflow holes. The plastic containers I am using have a convenient handle which makes for a good place to put them.

Picture 3
Cover the small drain hole with the larger sized gravel. This is done to keep the small pea gravel from clogging it.

Pictures 4 and 5
Go ahead and fill the container with the pea gravel. The container is pretty heavy when it's full, so you'll want to have it in position before you top it off.

Pictures 6, 7, and 8
Do the same thing with the overflow holes that you did with the small drain hole. Cover them with a layer of larger sized gravel and then put the pea gravel on top.

Note: You may want to test the system out with the pump first before these are covered so that you can be certain that they drain the water out fast enough.

Step 6: Adding a Support Wire

Depending on how sturdy your plant containers are, you may need to add support to help them hold up against the weight of the pea gravel.

Just drill a 1/8" hole in the middle of each side and run a wire between the two to strengthen things up.

Step 7: Setting Up the Pump and Hose

The only thing left to do before the system is finished is to set up the pump and run the hoses into the plant containers.

You'll need three pieces of hose and a 1/2" T-connector.

There isn't much I need to say here, so I will let the pictures do the talking.

Step 8: Misc. Information

Now that I've covered building the system, I'm going to go ahead and give some information on using it. (I'm just putting things down in the order that I think of them.)

At this point I should mention that I am by no means an expert. I'm just a hobbyist who is relaying his experiences. (Maybe I should have said that at the beginning. : )

Setting the Timer
Here is the schedule for my digital timer. It turns the pump on for 3 minutes every two hours between 7:00AM and 7:00PM. From what I've read, this schedule might be a little excessive, meaning that the plant containers are filled and drained more often than they need to be. However, my plastic containers are on the shallow side, and the plants suck up a lot of water. In 3 days, they will go through about 5 gallons, even more when it's hot outside.

I would experiment with the schedule some, but the timer is such a pain to program that I leave it alone. : )
////[ON]/////////[Off]/////
| 7:00AM | 7:03AM |
| 9:00AM | 9:03AM |
| 11:00AM | 11:03AM |
| 1:00PM | 1:03PM |
| 3:00PM | 3:03PM |
| 5:00PM | 5:03PM |
| 7:00PM | 7:03PM |

Float Valve
Like I mentioned above, the plants go through a lot of water, and the reservoir needs to be topped off regularly. I need to add a float valve sometime, but haven't gotten around to it yet. I'll have to try the "Hydroponic Float Valve" instructable when I do.

Nutrient Solution
When the plants are first starting out, I use a hydroponic solution that has (10-8-14) N-P-K. Once they start to flower, I use (3-35-10) N-P-K. This supposedly increases fruit production while slowing leaf growth. If you're growing plants like lettuce though, you'll want good leaf growth, so stick with the (10-8-14).

For this reason, you might want to have two separate systems. One where leaf growth is encouraged, and another where fruit growth is encouraged.

Over Planting
As a test, I once put 1 zucchini plant and 4 cherry tomato plants all inside one container. It had its own 15 gallon reservoir, but I thought that the plants would eventually show some signs of stress. Surprisingly though, they did quite well. I wish I had the pictures still, but they were among the few that weren't backed up when my hard drive decided to fail.

Step 9: Expanding the System

Here are some ideas of how this system might be expanded. I haven't actually tried these, but I can't see why they wouldn't work. If only I had the room. : (

Picture 1
The easiest way to expand it would be to just set multiple containers next to each other and use a longer reservoir.

Picture 2
Another idea would be to stack them end to end. Keep in mind though that the pump can only pump water so high. The GPH also decreases the higher you go.

Picture 3
You could also combine the two and go for the super mega deluxe system.
Muah-ha-ha-ha-ha.
(Ok, that might be too big. You wouldn't even be able to reach the plants in the middle.)

Picture 4
I need to get a life.