Flood and Drain Technique

Flood and Drain Hydroponic system As the name implies this technique involves flooding the growing table with nutrients and then letting them slowly drain back into the reservoir.
There are many commercially available systems, these are good to provide you with design ideas for your own Homemade Hydroponic flood and drain system.

Basic Design

The nutrient solution is pumped from the reservoir under the grow table and then slowly drains back into the reservoir through a drainage pipe of holes.  The pump is only run for enough time to fill the grow tray to the top of the overflow pipe, this needs to be done frequently enough to ensure that the plants roots stay moist.  Plants can be directly planted in aggregate in the grow tray or be in pots sitting in the grow tray.

Design Considerations

  • It may be necessary to change the frequency and length of time the pump is running as the seasons change to ensure that the plants are kept moist
  • The grow tray needs to be above or partially above the nutrient reservoir
  • The nutrient needs to be kept in a dark reservoir to stop algae growing, you can paint the outside of the container to stop light getting in
  • Ensure that the pump stays covered with nutrients when the grow tray is fill to stop the pump motor overheating
  • The addition of an air pump provides good aeration to the plants roots

Design Components

Reservoir

The size of the reservoir is dependent on the size of the grow tray you are going to use, the reservoir should be large enough to fill the grow tray to the overflow height and still leave the pump covered with nutrients.  It is recommended that you use a fish tank air pump to aerate the nutrient solution in the reservoir.

Ensure your reservoir does not let light in and that it is not susceptible to corrosion.  Good reservoirs are made of plastic, glass or stainless steel, other materials are fine if you use a plastic liner.

Grow Tray

The grow tray would ideally be made of plastic and can either sit partially inside the reservoir or on top of it.  Ideally the grow tray would be at least 10cm deep to provide plenty for aggregate or pots to be places and to be completely flooded with the nutrients.

Pump

You will require a submersible pump, the pump sits on the bottom of the reservoir tank, attach a pipe to deliver the nutrient to the grow tray.   The pump should be on a timer that will run for enough time to flood the grow tray to the top of the overflow,  the frequency that the pump needs to run will need to be determined by how quickly the aggregate drys out.  The aggregate should remain moist with little nutrient sitting in the bottom of grow tray.

Overflow Pipe

The overflow pipe is simply a section of plastic pipe that goes through the bottom of the grow tray.  The top of the overflow pipe should be at the maximum height that you want the nutrient level in the grow tray to be at when the tray is in its flooded state.

Drainage Holes

There are several ways to drain the grow tray back into the reservoir.  If the grow tray is sitting on top of the reservoir, simply drill some small holes in the bottom of the grow tray.  It is also possible to put small holes in the side of the overflow pipe.


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