How does an Ebb-flow system work?
Like the NFT System and other hydroponic systems, the essential functionality is circulating water from a reservoir to the plants which are embedded in a grow medium. Whereas the NFT system houses the plants in pipes and let the water run through the pipes. The ebb-flow system has instead a big grow tray, which is flooded with nutrient solution. The tray is connected to the reservoir with an overflow drain, therefore after flooding the tray, excess water drains back into the reservoir. This creates circulation which brings oxygen into the water and flushes also old nutrient solution out of the tray. The plants are placed in the tray, and their roots have direct access to the nutrient solution.
The grow tray is an essential part in this system, there are different versions possible. Especially when it comes to the grow medium. You can fill the whole tray with clay pebbles or you could use any other grow media or essentially anything where the roots can get hold. Because there is always a minimum amount of nutrient solution in the tray, a water-soaking growing medium is not necessary. Another important aspect of the grow tray is the overflow tube, in most designs the reservoir is directly under the grow tray, whereas the overflow tube is simply a tank connector which leads the water down. There is also the possibility to work with valves to have a better control over the ebb and flow behavior of the tray. Usually this is not necessary. Because the tray is completely filled with grow medium it might be necessary to support heavier loads, because grow medium and water plus the plant roots can become quite heavy.
Having a usually bigger grow tray with a lot of grow medium in the ebb-flow system supports also plants with more roots or plants in need for more hold like high-growing fruits or vegetables. Also you can freely chose the position of the plants.
The reservoir in an ebb-flow system is quite comparable to the reservoir of other systems like the NFT-system. However while ebb-flow systems can be quite big and also incorporate a constant water level, the reservoir must scale accordingly. Like in other systems the reservoir should have a submersible pump which is activated through a timer. Because the reservoir is so comparable to other systems it’s also possible to share a reservoir with another system.
The overflow drain is the connection of the grow tray to the reservoir. It can be quite simple but can also be used to optimize the system further. A simple hole is in most cases good enough for a beginner’s system. Because the grow tray is full of grow medium it’s important to prevent the grow medium from being pulled down into the reservoir through the overflow drain. A typical prevention is to shield the drain with a pipe which has holes to enable water flowing through but not the grow medium.
The advantages of an ebb-flow system are manifold and clearly outweigh the disadvantages.
- Great for bigger plants: Depending on the depth and size of the grow tray, an ebb-flow system can easily house even bigger plants like fruits and vegetables, unlike in other systems the plants can stretch their roots throughout the grow medium and get enough hold to grow tall.
- Low cost: Setting up an ebb-flow system with all its materials can be rather cheap especially if you decide to improvise on the parts, reuse old parts and use for instance a cheaper grow medium.
- Nutrient abundance: The ebb-flow system maintains a steady amount of nutrients for the plants. The overflow drain prevents flooding the grow tray and thus damaging the plants and roots.
- Easy to build: Building an ebb-flow system yourself is not hard. There is no expert equipment and tools necessary like in other hydroponics systems, not even net cups are needed nor pipes. By reading this post you should be able to build a starter system.
- Easy to use: Setting up the system is actually the hardest part. After that the system needs just basic supervision and maintenance. Like in any system the nutrient solution in the reservoir must be checked and whether the pump is still circulating the solution.
- Not easily breakable: Plants can grow pretty wild in hydroponics, other systems which are based on pipes circulating the water can be clogged with roots, this is not likely to happen in an ebb-flow system, because there is only one overflow drain and it’s usually to big to get clogged. Also as mentioned previously, the grow tray cannot be flooded and thus not water is lost.
In the advantages we learned about the ease of setting up and using an ebb-flow system, however no system comes without disadvantages
- Solid structure: As we already learned, the ebb-flow can become quite heavy supporting such a heavy grow tray on top of a reservoir might require a more solid structure.
- Scalability: Whereas other systems like the Nutrient-Film-Technique is based on pvc-pipes which can easily be scaled vertically, this is not as easy with an ebb-flow system, the grow tray is typically bigger and heavier and vertically scaling it requires a very good structure. Most of the ebb-flow systems scale horizontally. Also the typical design requires the reservoir to be underneath the grow tray, scaling the grow tray then means equally scaling the reservoir.
- Cleaning: Between seasons it’s adviseable to clean the whole tray and also the grow medium thoroughly, to prevent harmful algae and fungus growth which damages the new roots in the new season.
if the grow tray is big enough almost any plant is suitable also plants in need for bigger roots like fruits and vegetables.