This is a diagram of an ebb and flow hydroponic system

What Is Ebb And Flow Hydroponics?

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The ebb and flow method, also called flood and drain, is one of my favorite methods of hydroponic gardening. Ebb and flow systems are easy to use and can be customized to grow just about any type of plant with great success.

Here’s what you need to know about the ebb and flow method of hydroponic gardening!

How Does An Ebb And Flow Hydroponic System Work?

hydroponic ebb and flow garage systemEbb and flow hydroponic systems can be set up in a few different ways but all work under the same concept.

The grow tray of an ebb and flow hydroponic system is slowly flooded with nutrient solution. The water pump is typically set up on a timer to flood the grow bed and specific intervals.

When the hydroponic solution reaches the desired level, the nutrient solutions flows over the outlet and back into the reservoir.  As the nutrient solution drains from the grow tray the roots are then exposed to the needed oxygen.

The grow medium stays moist from the flooding until the grow bed is flooded and the process repeats. This constant flooding and draining provides the plants with an abundant amount of oxygen and nutrients and promotes fast, healthy growth.

Ebb and Flow Hydroponic System

Ebb And Flow System  Bed Variations

Like most hydroponic methods and systems, ebb and flow systems can be set up to work in several different ways.

The grow medium can be filled with grow medium with plants grown directly into the grow medium. The grow bed could also be left empty with grow medium and plants instead placed in small pots that sit in the grow bed.

Different Ways Ebb And Flow Systems Can Drain

Ebb And Flow Kit

Most ebb and flow systems, are set up with an ebb and flow kit and work as I explained above.

The ebb and flow kits come with 2 bulkhead fittings; the inlet and the outlet. The inlet is short and the outlets typically have and customizable height to control the water level.

Bell Siphon

In another variation of the ebb and flow system, the water pump runs all the time, constantly filling the grow bed. To drain the water when it reaches a certain height, a siphon is used. There are a few different types of automatic siphons, the most popular being the bell siphon.

Using one of these “automatic” drains on your ebb and flow system allows you to run your pump 24/7, so there’s no need to use a timer.  Adding a “bell” to go over the standpipe drain of your system is also a method of creating a vacuum to drain your system. As the water goes down the standpipe and hits an elbow it creates a vacuum draining the system. When water breaks the vacuum, the system fills again.

Choosing The Best Grow Medium Ebb And Flow Hydroponic Systems

There are a few different factors that you should consider when choosing a grow medium for your ebb and flow system.

Water retention– Ebb and flow systems work best with grow mediums that retain some moisture but drain well. Lava rock and hydroton clay pebbles both have these characteristics.

If you’re growing root vegetables– Root vegetables will need to be able to push grow medium to form a mass. Hydroton is more suitable for this than lava rock. Other grow medium like a vermiculite/ perlite mix also works well with root vegetables. Remember that you will need a deep grow bed to allow a solid root mass to have room to form.

Weight/ buoyancy- Your grow bed should be strong enough to hold the weight of your grow medium and water. Since your grow bed is being filled with water, it causes the lightweight grow medium to float, disrupting the plant’s root system.

What grow medium I use– I prefer to use expanded clay pebbles in my ebb and flow systems. They are reusable, lightweight, and have good air-to-water retention. Clay pebbles work well in filled grow beds or when used in individual pots.

Large rockwool blocks also work well as a grow medium in ebb and flow hydroponic systems.


Ebb and flow hydroponics is an extremely effective hydroponic system for growing plants. It is versatile and customizable making it great for hobby hydroponic gardeners. If you want to learn about other hydroponic methods, check out this article on different hydroponic systems!

5 Answers

  1. Roy Radford
    November 21, 2018 at 4:31 pm

    Thank you for taking the time and trouble to prepare these articles. The flood and drain system you describe is very similar to my own though, being 80 years old, I’m old-fashioned enough to call it gravel sub-irrigation. (As did Dudley Harris more years ago than I care to remember!)

    One small point. Your diagram shows the growth tank being filled by a standpipe ABOVE the medium. As the old name implies, I feed from UNDERNEATH the medium, keeping the top inch or so (2.5 cm if you use these new-fangled Centigrade units! ) dry. This discourages molds and some bugs. Further, the system you show would NOT drain back through the pump, mine does as the feed is from underneath the growth tank.

    1. NoSoilSolutions
      November 22, 2018 at 8:06 pm

      Thanks for stopping by the site Roy! I actually designed this system in particular to be automatically drained with a bell siphon as opposed to using a timer on the pump. I wanted to be able to have the water come over the top so I can easily control the flow rate since bell siphons requiring some tweaking. I enjoy experimenting with the different auto siphons.

    1. NoSoilSolutions
      November 23, 2018 at 11:36 am

      The pipe that runs the water into the systems goes down a few inches below into the grow bed and the standpipe draining the bed starts draining when the water level is still several inches from the top. I really don’t have too many issues with algae or molds.

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