Basic Hydroponic system - EBB & FLOW system (6/6)

Date Posted:31 May 2017 


EBB & FLOW system

The ebb and flow hydroponic system (also called flood and drain) is the classic hydroponic setup. It is easy to understand, build and maintain. It's versatile and can accommodate pots of any size, or even rockwool blocks. 

Individual potted plants are arranged on a drain table or "growing bed" which can hold a few inches of water. Periodically, the nutrient solution is pumped in, flooding the holding bed. The plants are watered from the bottom through the drain holes in the pots.

After a few minutes of soaking, the pump cuts off, and the table drains, the nutrient returning to the reservoir below it. This flood-and-drain cycle repeats 2-4 times a day. Simple but very effective.


Plant containers in series design

This type of setup is most commonly used when many different containers with plants are being watered (flooded) at the same time. It's important to remember that the system with Ebb&Flow Flood and drain systems the plants (containers) to be flooded (watered) needs to be above the reservoir, like on a table top or bench. That way the water can flow back to the reservoir by simple gravity, and thus drain the system correctly.  

 

1.Flooding tray design

The flooding table/tray flood and drain (ebb and flow) system type setup is useful when you want to place plants in the system temporarily, need to be moving them around a lot, or Ebb&Flow Flood and drain table design starting plants to be placed in another larger system. Instead of flooding separate containers with plants in it, this method only floods one container. Usually, a shallow square or rectangle container that sits on top of a table. The reservoir usually sits directly underneath with easy access.  

Ebb&Flow Flood and drain table when floodedWater is pumped up from the reservoir into the flooding tray on one side and the overflow is on the other side of the flooding tray. That makes sure the water actually circulates from one side of the tray/table to the other. Like any flood and drain (ebb and flow) system, the overflow tube height sets the water height during the flooding cycle, and can be adjusted as needed. 

Ebb&Flow Flood and drain table when drainedThe plants are grown in regular plastic pots or baskets, and placed in the flooding tray like regular potted plants. However, unlike regular potted plants, hydroponic growing media is used to pot the plants instead of using potting soil. Once the plants get big enough, they can be transferred into a permanent hydroponic system. 

One downside to using the flooding table is the algae growth, and should be cleaned out regularly. Because the top of the tray is usually left open, light is allowed to get into the nutrient solution in the bottom of the tray, That allows algae to grow. The algae alone isn't really bad for the plants, but it does use up dissolved oxygen in the water.

 

2.Serge tank flood and drain (ebb and flow) system design

The surge tank type of flood and drain setup is useful when more vertical space is needed. Typically with flood and drain systems, the reservoir is always lower than the hydroponic Ebb&Flow Flood and drain systems with surge tank system. That's so the water (nutrient solution) can drain out of the system through gravity back into the reservoir through the overflow, and when the pump is off. But you can still set up a flood and drain system even when the water level in the reservoir is higher than the hydroponic system it's supposed to flood and drain back from. That is with the use of a surge tank.     

The surge tank type of flood and drain system costs more to build because there are many more parts needed. It works on the principal Ebb&Flow Flood and drains systems with surge tank in flooding cycle that water seeks its own level. In other words, the water height in one container will be the same in another container when they are connected below the water line. The surge tank serves as a temporary reservoir that controls the water height in all the containers with the plants in them and is only full during the flooding cycle.  

Ebb&Flow Flood and drain systems with surge tank in flooding cycleThe surge tank flood and drain (ebb and flow) system operates by pumping water (nutrient solution) from the much larger main reservoir into the surge tank when the pump timer goes on. As the water level rises in the surge tank, the water level rises evenly in all the connected plant containers at the same time. When the water level gets high enough, a float valve in the Ebb&Flow Flood and drain systems with surge tank in drain cycle surge tank turns on a pump in the surge tank. The pump in the surge tank then pumps water back into the main reservoir. At this time both the pumps are on (pump in the main reservoir, and surge tank). 

After the timer for the pump in the main reservoir shuts off, the pump in the surge tank is still on. The pump in the surge tank continues pumping all the water back into the main reservoir (draining the system) until the water level gets low enough. At that point, a second float valve shuts off the pump in the surge tank.

 


 

Pros and Cons

Advantages

1. Easy to Build - Ebb and flow systems are roughly on the same level of difficulty as water cultures, drip systems and the likes, which are quite easy to handle if you have the right set of plans. You don't have to be a hydroponics system expert to get an ebb and flow up and running.

2. Easy to Use - An ebb and flow hydroponics system is quite easy to use and manage, as it doesn't require a lot of technical knowledge to keep it running. Even better, if you're not building it yourself, it's almost plug-and-grow easy.

3. Nutrient Abundance - Since the ebb and flow systems work on a flood/drain concept, the grow tray will constantly get flooded with nutrient rich water, leaving them feeding off for as much as they want. This is also beneficial for plants that require heavy loads of water to work with, such as strawberries.

4. Low Cost - ebb and flow hydroponics system costs are usually very low in comparison to many other systems, because they don't require any high tech, expensive components that could make their prices skyrocket. Even better, if you're going to try and build the system on your own, you will get off quite cheaply.

 

Disadvantages

1. Higher Risk - There are several risks involved with using an ebb and flow system: the flood/drain component could malfunction, causing the flood of the area you've installed the ebb and flow in. Another risk is that of ruining your plant yields, due to the flooding mechanism. Because many plants require a lot of water on their roots, but need not get their corona wet, ebb and flow hydroponics systems can actually be dangerous to your plants. The strawberry is the most well-known plant that can suffer from this in an ebb and flow hydroponics system.

2. Breakdowns - Because the ebb and flow system is running with the help of a pump controller, which is usually prone to breaking down, the risk of the entire system breaking down is also higher than with many other system types.

3. Plant Toxicity/Deficiency - ebb and flow hydroponics systems flood the plants with water, allow them to suck up their required nutrients, then drain the water back in the tank. Over time, continuously draining the water will have salt building up on the roots or the growth media, which will block out certain chemical elements from reaching the plant, causing a deficiency.

4. Unstable pH levels - When water and nutrient solutions are drained back from the growth tray and into the nutrient container, the pH level of the solution changes dramatically. This can have devastating effects on your plants in time, blocking out certain chemical elements, or allowing others to run out of control and cause toxicities.

What you need to build a Flood and Drain (Ebb and Flow) system:

  • A container for the plant's roots to grow in.
  • A container (reservoir) to hold the nutrient solution. 
  • A submersible fountain/pond pump. 
  • A light timer to turn the pump on and off. 
  • Some tubing to run from the pump in the reservoir to the system to be flooded.
  • An overflow tube set to the height you want the water level.
  • Growing medium of some kind.

 

There are many different ways to build a flood and drain system, and they are very good for growing small to medium size plants. Even for growing large plants with larger flood and drain system designs. You can use just about anything to build one including buckets, tubes, 2 liter bottles, storage totes, water bottles, an old ice chest, trash cans etc.. Just about anything that can hold water can be used. The imagination doesn't stop there either, there are many ways to flood and drain the roots in the system too. Below are some examples of how the three most common ways used to flood and drain the systems work.  

Tip 1. 

Make sure there is a way air can get in the top of the overflow without spilling water out. A "T" connector with an extension that is a few inches above the water line will work nicely. This will keep air pockets from forming in the system and make sure it floods and drains properly.   

Tip 2. 

Make sure the overflow tube is bigger than the water inlet tube from the pump. Otherwise because the water is only going out through gravity, and water is coming in through pressure from the pump, you could wind up pumping in more water than what is going out the overflow. That would lead to water building up and spilling out the top of your system, unless you reduce the pressure (volume) from the pump.  


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