The Flood and Drain Hydroponics System

The Flood and Drain hydroponics system (also called Ebb and Flow) is a method which is very popular among growers. It’s reasonably inexpensive to set up one of these systems, and they can be very versatile.

You can easily expand the number of plants in this system, so it is popular with growers who use hydroponics commercially.

What is the Flood and Drain Hydroponic System?

The Flood and Drain hydroponic system is very reliable. The plants grow in pots filled with an inert growing medium that keeps the roots in place so that the nutrient solution has easy access.

This method alternately floods the whole system and then drains away. This cycle is then allowed to repeat itself over and over.

There is a growing bed or table on which the pots containing the growing medium sit. Some growers use a combination of growing media which absorbs the nutrient solution efficiently and evenly.

The solution from the reservoir can flood the system for between five and ten minutes. As the reservoir is beneath the table, your nutrient solution can drain away by gravity. This setup forms a closed system that the solution can recycle through.

You should monitor the pH levels often when the nutrient solution returns to the reservoir, as eventually, this will need replacing (we recommend once a week). Check out the Bluelab pH Pen here.

The frequency of flooding depends on the capacity of the growing medium to retain liquid. If the growing medium is liquid-retentive, the flooding stage can occur once a day. With a less liquid-retentive growing medium, the frequency will need to increase, to as many as eight flood sessions per day, each lasting between five and ten minutes.

The solution pumps from the reservoir stored beneath the system so that it will drain away with gravity.

You can have one to several plants in a Flood and Drain system, each in a pot and joined in a series. A timer controls the pump. The nutrient solution pumps into the system until the height of the pre-set overflow tube is reached, allowing the plant’s roots to soak in the solution. This overflow tube should be about 5cm below the growing medium’s surface.

Once the nutrient solution has reached the level of the overflow tube, it will drain back into the reservoir, and the whole process will begin again. The overflow tube has two functions: to ensure that the plants’ roots are well irrigated and that it does not spill over. As soon as the pump switches off, it will drain back into the reservoir.

Equipment Needed for a Flood and Drain Hydroponics System

You’ll need the following equipment and material for your Flood and Drain system:

• A pot for the plant’s roots to grow
• A container for the reservoir
• A timer to activate the pump
• A submerged water pump
• Tubing from the reservoir pump to the system
• The overflow tube, which you’ll need to set to the optimum height
• Growing media (possibly in combination)

Flood and drain systems are helpful if you plan to grow plants of any size. The larger the plant you’re growing, the larger the scale of your system.

You should ensure that air can get to the overflow without having the nutrient solution spill out. You can use a T-connector to prevent air pockets from forming and ensure it works properly.

You should also ensure that your overflow tube is wider than the inlet tube from the pump. Otherwise, there’s the danger of pumping in more nutrient solution than is leaving your system through the overflow pipe, leading to the solution spilling out.

Variations of the Flood and Drain Hydroponics System

If you have a relatively large number of plants in their pots to be flooded and drained (at the same time), you’ll have the plant pots connected in series. The plants are permanently placed above the reservoir (except when using a surge tank – see below) so that gravity can drain the nutrients.

The plants’ pots are connected, each flooding evenly and simultaneously. The system needs only one overflow tube, as this will control each plant pot. The height of this tube will determine the level at which the nutrient solution fills all the pots. This simple function means you can adjust the level for all the plants’ pots by adjusting the height of this tube.

Alternatively, in a variation called the Flood Tray method, you can use just one tray to put all the plant pots in and allow this tray to flood instead of flooding each plant in individual pots. This method involves a large tray, usually rectangular, which sits on the table above the reservoir.

The solution pumps from the reservoir into one side of the flood tray, while the overflow tube is on the opposite side. Again, the overflow tube height determines the solution’s level throughout the flooding cycle.

There’s another alternate Flood and Drain system called the surge-type; this can be pretty useful if space is at a premium. With a typical system like this, the reservoir containing the nutrients is always lower than the rest, allowing the drain part of the cycle to take place entirely by gravity.

However, using a surge tank means the reservoir can be higher than the table. This type of Flood and Drain system is relatively expensive to build because more parts are necessary.

The principle of the surge tank is that water will seek its level, so the level of nutrient solution will be the same in all connected plant pots. Here the surge tank acts as a temporary reservoir and is full only during the flood part of the cycle.

The nutrient solution pumps from the reservoir into the surge tank, and then a timer activates it. As the nutrient solution level rises within the surge tank, it simultaneously rises in all the plant pots. A float valve will turn on another pump in the surge tank once the level reaches a predetermined height. This pump will pump water back into the reservoir. This feature means it doesn’t need to rely on gravity and can be above the rest of the system.

When the timer for the reservoir pump switches off, the surge tank pump is still on, and it continues to pump all the nutrient solution back into the reservoir, so the drain part of the cycle takes place. Another float valve will then operate when the level gets to a predetermined low point, and this will switch off the surge tank pump.

As you can see, this variant of the Flood and Drain system is a bit more complicated than the traditional method. For this reason, it’s best when the amount or configuration of space is relatively small.

Pros and Cons

As with all the six types of systems, the Flood and Drain hydroponic system has advantages and disadvantages. These are as follows.

Advantages

• Some consider flood and Drain an excellent place to start with hydroponics.
• The use of a timer means that little manual effort is needed
• Comparatively easy to set up
• Only a few components are necessary
• The plants grown by Flood and Drain are relatively strong because the cycle is advantageous for the plant’s growth cycle. Roots receiving nutrients from below become healthy and robust, while the draining part ensures the plants have plenty of oxygen.
• All the components are cheap and easy to replace
• You can switch from one growing medium to another to see which works best.

Disadvantages

• The potential for algae growth occurs when the light enters the nutrient solution at the bottom of the flood tray. Algae, while not damaging your plants, nevertheless uses up valuable oxygen, depriving the plants of that crucial element. For this reason, you should clean the tray regularly.
• Reliance on a continuous electricity supply means that any power cut or outage will cause your plant’s roots to dry up fairly quickly. This event could be disastrous and might kill your harvest altogether.
• The system favours small- to medium-sized plants, so it’s best to consider something other than this type of system for larger plants.
• Minerals may build up over time and hinder the nutrients from reaching where necessary. Look out for such build-ups of minerals, and if you see this happening, you should remedy it quickly by cleaning thoroughly.

In conclusion, you should consider all the factors when deciding which hydroponic system to choose. The Flood and Drain system is adaptable and easily scaled up, so it is a good option for a commercial hydroponic system.