Hydroponic Growing Techniques

How To Build Your Own Flood and Drain (Ebb and Flow) System

Master hydroponicist and chilli fanatic, Jukka Kilpinen, shows us just how easy it is to custom build your own flood & drain (ebb & flood) hydroponics system!

After growing chilli plants with different hydroponic systems for nearly ten years, one hydroponic system still stands clearly ahead of them all: Flood & Drain aka Ebb and Flow.

Before using it or seeing in action, it may seem a little complicated but after you get it, I believe that it's probably the most simple system there is!

Flood & drain offers many advantages:

- efficient yet still very simple! Gives unbelievable crops with decent nutrients and in a location with plenty light.

- possible to use any growing tray sizes you want with the same principle from trays for tiny seedlings through to systems several meters long! You don't need super powerful pumps for flood & drain either, any low-power aquarium pump will do, as the objective is simply to have the growing container flooded with nutrient solution for a few minutes or even seconds.

  • Plants can be transferred directly to flood & drain systems after germinating.
  • Flood & drain develops very strong decent roots with chilli peppers that make it perfect for transferring the plants when needed. I believe that flood & drain achieves this much better than any other hydroponic systems.
  • You can grow all of your plants in one system and easily re-arrange or transfer them to other hydroponic systems or even soil.Nno hydroponic pots of any kind are needed.
  • Flood & drain's simplicity makes it very reliable so plants can be left alone for even weeks. (If the nutrient reservoir is big enough.)
  • Easy to integrate into balcony, a table or growing corner. It's an incredibly versatile system that can be built as you like to use it and as you want it to look.
  • Very easy to maintain, if you build your ebb properly, changing nutrient solution after each two weeks or so will be very easy and quick.
  • Very safe which makes it ideal for indoor growing. Properly planned flood & drain won't leak the nutrients to the floor of your apartment as the growing container rests directly on top of the nutrient container. All inlets and holes are in a place where dripping doesn't matter.
  • Flood & drain is also ideal for indoor growing as it's very silent even when the pump runs.

Okay, let's get started with some planning:

First you need to work out what kind of space you will have available for you plants so you can scale your system accordingly.

It's also important to remember that your plants can grow HUGE meaning high water and nutrient requirements! A smaller reservoir will mean that you need to add water more often.

No matter how small or big a system you build, the principle is exactly the same as shown on this building example.

The growing container (the upper part) can be any shape you wish. For practical reasons, sizes like 60 x 60cm or 80x80cm and bigger are a good plan. If in doubt go for squares or near square rectangles. Be sure to leave adequate space around the system. Your chilli plants will thank you for it.

For bigger systems I would recommend a long (but not too wide) system. My "monster" 30 cm x 5 meter flood & drain system has been ideal for efficient and easy growing. 

Back to the basic principle: the plant container (upper part) will be filled with expanded clay pebbles. Some growers mix in 50 / 50 diatomite too for added plant-available silica. (If you go this route, be sure to reduce the frequency of your irrigation as diatomite is more absorbent than clay pebbles.)

I usually start my seedlings off by germinating them in rockwool cubes and then transferring into rockwool blocks. Sometimes I plant aeroponic cuttings (without rockwool or any other propagation media) and that works also well. Just be extra careful with those roots when transplanting.

How the System Works

The timer is first set to pump nutrient solution to the upper tray twice a day.

It floods the upper tray and waters the roots and expanded clay balls with nutrient solution. After a minute (or any time suitable for your ebb) the timer will turn off the pump and the nutrient solution drains back to nutrient container back through the pump. (Make sure your pump allows water to drain back through it. Don't worry - those beautiful people at your local grow shop will sort you out.) An overflow drain ensures that any excess water drains back to reservoir before the expanded clay starts to flow. Best practice is to set the timer to stop the pump when the water reaches overflow tube. A digital (rather than segmental) timer affords the grower more accuracy in setting irrigation times. The overflow should be adjustable so as to make the incoming nutrient solution deep enough to reach the roots of the plants.

Errrr … that's it!

So why it is so efficient then?

First of all, with a digital timer, the watering can be adjusted for different chillies as some like it more wet and some like more dry conditions. And of course its good to water more during the summer when it's hot and less during the winter.

Flood & drain seems to be especially ideal for growing chilli peppers, tomatoes, peas, melons etc. Allowing the growing media to dry out more between irrigation cycles encourages your plants to flower. Keeping the media wetter will generally produce a more vegetative effect.

Second: Whilst some growers are building very complicated aeroponics systems at home, I'm not so keen as you need expensive pumps that consume more electricity and tend to also make quite a bit noise. 

When your root zone is flooded in a flood & drain system, any stale air is forced out. When the system drains, fresh air in pulled back in. Happy, happy roots! Another reason why it's so important to have a well-ventilated growing environment.

Anyway, back to the build. You need to find an appropriate container to house your plants in. The one chosen here works very nicely as an example. Transparent containers (for either the upper or lower tray) may look quite funky but they are far from ideal because roots and your nutrient solution don't like light at all. This can be prevented by covering the container with plastic but why not just go for an opaque container in the first place? :-)

Plastic Box used for reservoir in DIY flood and drain hydroponics system - transparent boxes are used here for presentation purposes - in practice you should choose opaque boxes to protect the roots from light

Here's the two-part box chosen for this example. See how the top box sits nicely on top of the bottom box. You can use two completely different boxes and just place the growing container on top of the reservoir or even use table in between.

Here are other parts used in this project:

Parts for DIY Flood and Drain system

Any place where water flows will need to be filtered using a suitable material like plastic mosquito netting.

Two pieces of hose. Use thinner for the pump and thicker for the overflow.

Overflow hose with a cheap faucet piece. As mentioned earlier, you can also use plastic mosquito net instead if you wish.

EcoPlus Eco 185 Submersible Pump for Flood and Drain systems

Here's the submersible pump used with this Flood & Drain.

This same pump works just as well with a much, much bigger Flood & Drain system.


A drill bit attached to this cordless drill shown here is ideal for drilling holes into the upper tray. The cut needs to be very smooth so it's easy to adjust the overflow tube when necessary.

Okay - so you have your stuff in place. Now it's time to build the system!

FIRST - you need to drill TWO holes through the bottom of the container. One for the inlet (water in) and a slightly larger one for the overflow (water out.) 

Drilling the hole for the inlet.


For the inlet part the hole doesn't have to be exact, just drill with this piece and try to fit the inlet when the hole looks close enough. If it doesn't quite fit, make the hole a tiny bit bigger and try again until it slots in nicely.

Here's the inlet in place on the growing container.

Drilling the hole for the overflow.

Drill the hole for the overflow. In this case, this one has to be more exact. In other words, it has to be just smaller than the hose.

When the hole for the overflow is done, push the overflow tube through the hole and voilá! You've got yourself an adjustable overflow! It's that simple!

If you accidentally make the hole too big, don't worry, just replace the overflow tube with bigger one. Actually, the bigger the overflow tube is, the better it will work!

Ok, so at this point, the system is almost done!

This is how it should look now from the bottom of the growing container.

Now cut a piece of the hose for the pump and inlet.

You need to estimate the length of the hose needed in between the pump and the outlet and attach it to the inlet.

Here's the pump attached to the inlet with a piece of hose.

At this point you can attempt to place the growing container on the nutrient reservoir to see if it fits. If the hose is too long, just cut piece by piece off it until it fits perfectly.

Okay, the actual work has been done now. Lets look at the system now:


The flood and drain system is now ready for growth media and nutrient solution! 

Now it's time to test-drive the system. Her "maiden flood," if you will!

Pour in your washed, expanded clay balls or a similar (preferably non-restrictive) growing media.

Make sure your clay balls are washed before you put them into the growing tray. I find it's easiest to wash them in the bag they come in, just poke some holes at the bottom of the bag and run water through until the water coming out is quite clear (rather than brown and dusty.)

Washed clay balls added to the system.

Fill the reservoir with plain water, halfway or so, it doesn't matter at this stage.

Now you need to time how long it takes to flood the upper tray. Prepare to start a stopwatch (most mobile phones have them these days.) Turn the pump on! Start the stop watch.

Keep an eye on the water level then turn off the stopwatch when the water starts pouring from the overflow. Take a look at your stopwatch. This is the approximate ideal time needed to flood the upper tray.

Adjust the pump run times according to available light. If the light hits the plants at 8:00am, you can flood the growing container around then or maybe 30-60 minutes after. Then, for example, you can schedule additional floods at 12:00pm and at 4:00pm or 6:00pm or whenever the sun / artificial light fades out / turns off. There's no need to run the pump during the darker hours.

Side view of flood and drain DIY hydroponics system complete with growing media and water.

At this point, your system is ready for the plants!

Alternative arrangement: the grow chamber can sit perpendicular on top of the nutrient reservoir

You can move germinated plants or bigger seedlings into the system.

You can also use your flood & drain unit as seedling growing system if you wish.

I start ALL of my plants hydroponically which makes growing much easier and more fun.

 The actual planting is very easy. Just dig out some expanded clay and place the rockwool cube in place and cover it with expanded clay. This process only takes a couple of seconds!

As I mentioned earlier, an ideal amount of plants to grow in this system is 2-4. Just let the plants grow towards separate directions and support them if needed.

Most people who have tried this flood & drain system swear it's the best hydroponic system they've ever used! And who am I to disagree? There are so many positive aspects when it comes to growing your favourite plants in flood & drain and the yields are phenomenal!

Oh and one final word, if you can't be bothered to build your own system, there are loads of fantastic ready-to-use flood and drain systems available at your local grow store!

Happy hydroponic gardening!

For more info check out Jukka's website at: www.fatalii.net/growing/

Words: Jukka Kilpinen