Step 1: How does it Work?
An ebb and flow hydroponic system works by filling a container full of gravel with water and then letting it empty. (The water is, of course, mixed with nutrients.) A thin film will adhere to the gravel allowing the plant roots to gather nutrients even after the container has been drained.
Each act of filling and emptying is like a breath of fresh air for the roots. Filling the container removes the old air while emptying it draws in new air containing fresh oxygen. This is one reason why plants do so well in this type of hydroponic system, or, in fact, any system which creates a good supply of oxygen.
If you look at the first picture, you will see a pump at the bottom of the large container which stores the water between filling and draining (AKA "the reservoir"). A hose connects to this pump and splits off into the two containers which hold the gravel and the plants.
A timer turns the pump on several times throughout the day to fill the plant containers with water.
Holes are drilled into one end of the plant containers so that any overflow will drain back into the reservoir.
Note: The water must be able to drain out of these holes faster than the pump can pump it in.
A small drain hole is drilled into the bottom corner of each plant container over the reservoir. This lets the water drain out. It is important not to make this hole too large.
Note: The water must not drain out of this hole faster than the pump can pump it in.
One end of each plant container is placed higher than the other end. This ensures that the water flows toward the small drain hole.