Ebb and Flow Systems of Hydroponic Gardens

How They Work and Why to Use Them

Ebb and flow hydroponic system filled with plants and clay growing medium

The Spruce / Kevin Norris

Ebb and Flow, also known as Flood and Drain, is one of the most widely recognized hydroponics systems. The versatile system is relatively low-cost to set up and requires an intermediate level of skill to maintain.

This method allows you to easily alter your garden, adding or removing plants as you wish without affecting any of the surrounding crops. Like other methods, the basic concept is very simple–plants are placed in a tray, which is periodically filled with nutrient-rich water pumped out of a reservoir below. The system uses gravity to return the water to the reservoir to be reused.

This action is normally done with a submerged pump that is connected to a timer. The timer is set to come on several times a day, depending on the size and type of plants, temperature, humidity, and the type of growing medium used.

This system seems complex to beginners because it involves so many different components, but they all come together quite easily and can be assembled in very little time. Once assembled, this system needs little maintenance and produces plants efficiently with very little electricity or water use.

Basic Components

The basic components of the Ebb & Flow system are the plant tray, reservoir, submersible pump, and timer.

The Plant Tray

The plant tray—also called a flood tray—is a large, shallow container on a tall stand. The plants are placed in the tray, in perforated pots filled with a growing medium such as Perlite. The pots chosen for seedlings should be about twice as deep as the flood tray. The flood tray is pumped full of nutrient-dense water from the reservoir below. The water flows up through the bottom of the pots to the roots of the plants. The water is then drained back out, allowing the roots to become completely dry and oxygenated before flooding again.

Ebb and flow hydroponic system plant tray filled with plants and growing medium

The Spruce / Kevin Norris

The Reservoir, Submersible Pump, and Timer

The reservoir is placed directly below the flood tray on the stand. It is connected to the tray via a fill tube and a drain tube. The fill tube attaches to a submersible pump with a timer, which controls the flow of water up into the flood tray. The drain tube allows gravity to pull the water back into the reservoir after flooding so that the water can be reused.

The same water can be used for about a week at a time. When it is time to change the water, make sure to renew the nutrients. The submersible pump with a timer allows for control in this type of system because you can customize the length and frequency of watering based on your gardens' needs.

Ebb and flow hydroponic system water reservoir, pump and timer

The Spruce / Kevin Norris

The Importance of Cleaning the System

It is very popular to grow certain plants like tomatoes and beans in these systems because trellises can be attached directly to the plant tray's stand. Because of the constant movement of water, it is important that you thoroughly scrub, clean, and sterilize your growing medium, reservoir, pots, and plant tray after each growing season. It is not uncommon for harmless algae to grow on the surfaces, but improper cleaning can lead to mold and insect infestations that could ruin your future harvests.

Why Choose an Ebb and Flow System?

Ebb and Flow systems can seem daunting to beginners, but they are perfect for the hobbyist with a bit of experience who is looking to "upgrade" their system. This type of setup allows for more options than some beginner kits such as lettuce rafts. If your tray is large enough, you can plant almost anything.

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  1. Hydroponics. Oklahoma State University Extension

  2. Simple Hydroponics. Penn State Extension