Build Your Own Flood and Drain Hydroponics System

Flood and Drain (Ebb and Flow) hydroponic systems are very popular with home hydroponic growers. They are easy to build and you can use household materials to put together a working flood and drain hydro system. Similar to drip systems, ebb and flow systems can be customized and build to fit any space both indoors and outdoors. When set up correctly, plants grow very well in flood and drain hydroponic systems. The concept of flood and drain systems is simple and self explanatory. Plant’s root system is flooded with the nutrient solution on a timer, once the timer turns off, the excess solution is drained back into the reservoir. This process continues at a set interval throughout the day. Unlike other systems, the root system isn’t constantly exposed to the nutrient solution.
Flood and Drain Hydroponic System - Ebb and Flow Hydroponic System
The growing tray of the flood and drain system holds the plant containers. It can be just one plant or many. The timer turns on the pump, nutrient solution is pumped from the reservoir to the growing tray using a submersible pump. Nutrient solution fills (floods) the tray until it reaches the height of the overflow to soak the plants’ roots. The overflow should be set 2 inches below the top of the plant’s growing media.

When the water/nutrient solution reaches the overflow height, it drains back to the reservoir where it’s recirculated back through the system. The overflow sets the water level height in the flood and drain system, and makes sure the water (nutrient solution) doesn’t overflow the top of the system while the pump is running. When the pump timer shuts off, the water siphons back down into the reservoir through the pump, draining the growing tray until the timer turns on the pump at the next interval.

Flood and Drain (Ebb and Flow) hydroponic system components:

  • Permeable container(s) or pots
  • Container/growing tray for the plant’s roots to be flooded
  • Reservoir to hold the water/nutrient solution
  • Submersible pump
  • Timer to turn the pump on and off
  • Tubing to run from the pump to the reservoir to the growing tray
  • Overflow tube set to the height you want the water level
  • Growing medium

There are different ways to build flood and drain systems, and these systems are great or growing small to medium size plants. You can use anything that will hold water to build a flood and drain system including buckets, tubes, empty 2 liters, storage totes, water bottles, trash cans etc. If you are looking to grow larger plants, there will be some tweaks you’ll probably need to make and plan for when considering or building an ebb and flow system for large plants.

#1 Allow air to get into the top of the overflow without water coming out. Add a ‘T’ connector that extends a few inches above the water line to make sure that air bubbles don’t form so that the draining process takes place smoothly and properly.

#2 The overflow tube must be bigger than the water inlet from the pump or the system will pump in more nutrient solution than the overflow can drain. This will cause your system to literally flood, and it won’t stop until the reservoir is empty. You could also avoid this by reducing the pressure (volume) from the pump.

The 3 Types of Flood and Drain Hydroponic System Setups

Plants in series
This is the most common flood and drain setup, all plants are watered/fed at the same time. In this setup all plants need to be above the reservoir on a table or bench. This allows the water to flow back to the reservoir by gravity to drain the system.

First, the containers are connected through tubing so that all plants are flooded evenly at the same time. There is a single overflow tube because all plants are flooded together on a single tray or bench. This setup is only recommended when you are growing the same plant or type of plant in same growing tray or bench.

Flood tray
This type of flood and drain setup is useful if you need to move plants around or possibly move them into a larger system later in there lifecycle. Since each plant is independent of the others, each plant uptakes different amounts of nutrient solution based on its size, position relative to light, etc. You will need to adjust your overflow accordingly based on how you’re plants are consuming nutrient solution and water.

Plants are grown in plastic normal pots or net pots and position sporadically around the table. The advantage is that once plants are grown to a certain size they can be transplanted to a larger system, outdoors or to soil. This setup is very versatile with what you do with your plants. It also allows the flexibility of growing many different varieties and species on a single tray.

One major downside to a flooding table is the potential for algae growth. You should clean your tray and reservoir regularly to try and avoid potential problems with algae. Algae won’t kill your plants, however it invites pests and also steals oxygen from your plants.

Ebb & Flow
Serge tank type setup of flood and drain is useful when growing taller plants. The other flood and drain systems (ebb and flow systems) position their reservoir below the growing chamber so the water (nutrient solution) can drain out of the system through gravity. The serge tank flood and drain hydroponic system allows the water level in the reservoir to be higher than the hydroponic system it’s flooding.

Serge tank type of flood and drain systems are more expensive, mainly because there are more parts and pieces to the system. Water seeks it’s own level – the water height in container A will be the same in container B when they are connected below the water line. A serge tank is a temporary reservoir that controls the water height in all the plant’s containers. The serge tank is only full during the flooding cycle.

  1. Nutrient solution is pumped from the reservoir to the serge tank
  2. The water level rises in the serge tank while rising simultaneously rising evenly in the plants’ containers
  3. When water in the serge tank reaches the desired level, a float valve turns on a pump in the serge tank
  4. The pump in the serge tank pumps water back to the reservoir
  5. At this time both the pumps are on (pump in main reservoir, and serge tank)
  6. After the timer for the pump in the main reservoir shuts off, the pump in the serge tank is still on.
  7. The pump in the serge tank continues pumping all the water back into the reservoir (draining the system) until the water level gets low enough
  8. At that point a second float valve shuts off the pump in the serge tank.

Flood and Drain Hydroponic System - Serge Tank Setup
The serge tank setup can be very difficult to understand especially when reading however the concept is pretty simple, take a look at the diagram above to get a better understanding of the ebb and flow hydroponic system works with a serge tank.