Hydroponic Flood & Drain Cycle

Flooding

• The flooding, or flow, part of the hydroponic flood and drain cycle occurs when the plant container is filled almost to the top with the nutrient solution. The solution normally fills the container to within about an inch of the top of whatever growth medium -- which commonly is perlite, silica rocks or clay pellets -- is being used. It stops before the top of the medium gets wet to reduce the chances of a film of algae growing in the container. The flood stage normally takes 10 minutes or less.

Draining

• Once the plant container fills, it is allowed to drain completely, a process that takes about half an hour. This is the "ebb" referred to in an ebb and flow system. While the water is in the container, it soaks the growth medium and the plants' roots, giving the plants direct access to all necessary nutrients. After the liquid is out of the container, the plants continue to benefit from the residual nutrient solution. The roots also get exposed to the air, which is essential to the plants.

Automatic Setup

• An automatic flood and drain system is set up with the planters in a series, so that one drains into the next, or with all of the plants contained in a single container, such as a tray. The last container to be filled with nutrient solution drains into a storage tank that holds the nutrient solution until it is needed. Inside the storage tank is a submersible pump, such as the type used in ponds, that is capable of pumping the liquid out of the tank and into the plant container as needed. The pump is connected to a timer, which regulates the system.

Manual Setup

• In some cases, a manual flood and drain system may be preferred over an automatic one. This is especially true if the hydroponics setup is installed in a remote area where there is no electricity available, or if the user prefers not to invest in extra equipment to run the cycles. The manual operation is similar to the automatic system, except that it does not use a pump or times. Instead, nutrient solution is poured manually from a watering can into the container filled with growth medium. Either the liquid is allowed to drain out onto the dirt to evaporate or it is captured in a tray for reuse. This system is inconvenient in that someone must flood the container regularly, several times per day, but it will still provide excellent results.