This instructable gives details on how to build an ebb and flow ( or flood and drain) hydroponic system for a decent price! It cost me less than US$100. An ebb and flow hydroponic system works as follows.

Plants are put into a grow box in an inert medium, nutritious water is then pumped into the grow box from a reservoir several times a day, flooding the entire grow box and plants roots. The grow box then drains all the water. This process happens several times a day which provides the plants roots with nutrition as well as the air it needs. The process of flooding also washes away any salts or unneeded material from the plants roots.

This system of hydroponics is used by several hobbyists as well as commercial growers.

The system described here can be used outdoors or indoors with the correct lights. (although I haven't tried using it indoors yet)

Step 1: Construction Materials

The following is a list of materials needed to make an ebb and flow (flood and drain) hydroponic system

2 x cat litter boxes, or something similar.
1 large reservoir, I used a 110 litre black (to reduce algae) plastic storage box.
1 x pump, check your pump head to make sure it will work, I am using a 650 litre / hour pump.
1 x digital display plug timer.
4-5 m of 12 mm PVC tubing.
4 x 12 mm to 1/2 inch irrigation elbows.
2 x 12 mm irrigation T pieces.
8 x rubber washers.
2 x 12 mm pop up sprinkler.
2 x 12 mm plastic nuts.
10 m 40 mm PVC pipe.
8 x 40 mm PVC pipe elbows.
8 x 40 mm PVC T pieces.
Plumbers tape.
Some shade cloth
Optional piece of chipboard
A few nuts and bolts

Step 2: Tools Required

The following are the tools that I used however use what you have available to you .

Drill.
Various drill bits
Craft knife.
Hack saw / angle grinder.
Measuring tape.

Step 3: Preparing the Grow Boxes

The two cat litter boxes mentioned earlier will be used as the grow boxes. The following are the steps taken to prepare the grow box.

The first step is to drill 2 20 mm holes through the litter boxes, one for the water to flow in from the pump (and out when the pump is off) and the second hole will be for an overflow. Where you place these is up to you, I chose to put them in the middle on each end of the grow tray ( see image 1).

Wrap plumbers tape around the threaded side of your 12 mm irrigation elbow, place a rubber washer on and push through the drilled hole. Do this for both drilled holes (see image 2).

I used pop up sprinklers as the overflows, the reason was I was unable to find any other threaded fittings that fitted on the 12 mm elbow. I disassembled them and used the case only ( I use these sprinklers in my garden anyway so internals won't go to waste) I also cut them to the correct overflow height(see image 3 and 4). I screwed this onto the 12 mm fitting inside the grow box again with a rubber washer (see image 5 and 6).

Finally I used the plastic 12 mm nut and shade net with a rubber washer to attach the other elbow where the fluid will flow in (see image 7).

I also added shade net into the overflow so no big particles get stuck in the system (image 8).

Step 4: Preparing the Reservoir.

The reservoir will store your highly nutritious H20 for you plants.

The submersible pump needs to be placed inside the large reservoir, and 3 holes need to be drilled into the lid. 2 12mm holes need to be drilled for the pump output and the other for the overflow back into the Reservoir (see image 2). The third hole needs to be drilled for the pumps power cable to exit the tank. I placed a slit on the side of the tank( see image 3 and 4).

Step 5: Building the Frame

Image 1 shows the design of my frame for the project, we wanted the grow boxes to be at a nice height so settled on ±1 m. The width and length were dictated by the size of the grow boxes. 40 mm PVC pipe was used to build the frame.

Step 1 of the frame building was cutting the Pvc to size. Chances are your grow boxes will be slightly different sizes so you will need to measure and calculate the length you need. My exact dimensions are shown in image 1. Image 2 and 3 show me cutting pieces to size.

Image 4 shows me assembling with T pieces and elbows.

Image 5 shows the completed top part of the frame.

Image 6 shows me checking that the reservoir fits and that grow boxes fit in the frame and image 7 shows the completed frame with grow boxes in place.

During my first tests I wasn't happy with the weight of the cat litter boxes resting on the pvc alone. So I attached a piece of chipboard at the correct height across the width of the frame. (See image 8) I attached it by drilling holes into the chipboard and using some bolts I had at home to make a type of u bolt. (image 9)

Step 6: Completing the Plumbing

The pvc pipe was then attached to the grow box via the elbows (image 1). The two grow boxes overflow and input were joined using the t piece (image 2) and the inlet and overflow were fed into the Reservoir ( image 3).

Step 7: Timer and Grow Medium

The final step was to add the grow medium. I chose to use expanded clay, or hydroton. Then plug the pump into a timer and set the timer for how many times a day it needs to water the hydroponics.

I'm also not going to go into detail about nutrients used as there is a lot of info on the Web about hydroponic nutrients.
Mine is set to flood 5 times a day, and I currently have seedlings in the system. See the pictures above.

I am still very much learning so I don't know how well the system will work and what problems I will have. I will keep this instructable up to date as time passes.

Step 8: First Set of Changes Made

Hi all,

So I have made a couple of changed to my rig. My first change was that my reservoir was massive. Way to big so I have replaced it with a 25 l bucket.

This however also lead to an issue that was brought up before, and that was light contacting the high nutrient water. So I bought some white sheeting. It was $10 for 10 m x 1.5 m. I wrapped the entire frame in this to minimise the amount of light on the clear tubes and semi permeable bucket. This should hopefully stop any algae growth!

Thanks all for the favourites, comments and views! And watch this space, my next hydroponic instructable is coming soon.

Step 9: October 2015 Update

Due to persistent algae growth, I have had to make a few changes. I was getting worried that my plants weren't getting enough oxygen so had a bit of a rethink.

What ended up changing was that I changed the white bucket out for a darker coloured bucket that allowed less light through. I also covered the clear PVC pipes with black irrigation tubing, allowing no light to penetrate. Where there were still gaps I covered with black Duct Tape.