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How a Flood and Drain Hydroponics System Works

hydroponic media
hydroponic media

There are a number of different methods of hydroponics and each one operates a little differently from the others. Virtually all methods of hydroponics provide better results than growing in soil if well tended but some techniques are higher maintainence than others. We have selected the flood and drain method for our do it yourself hydroponics system because the system will be very easy to build, resistant to leaking, produce excellent results and be really simple to use. And best of all, if you follow the directions, it will be automated and require very little in the way of work to keep it going.

So How Does Our DIY Hydroponics System Work?

Its really easy to see how if you study our diagrams. Our hydroponics system is based around two plastic tubs, one will be our nutrient reservoir and the other will be our growbed. The growbed contains our plants which are grown in a suitable hydroponic media such as hydroclay (pictured above) or gravel that performs some of the jobs soil would do in a traditional garden. The media provides a place for the plants to anchor their roots and in a flood and drain hydroponics system the media should drain fairly rapidly so a large particle size is required. Definitely go for hydroclay, scorier or a similar volcanic media.

The Flood and Drain Hydroponics System and its Components

Underneath the growbed is the reservoir which contains the nutrient solution. The nutrient solution is really just fertilizer mixed with water that the plants can drink to get the essential nutrients and water that they need to grow. The reservoir must be at a lower level than the growbed so that gravity will allow the nutrient solution to drain back into the reservoir once the pump has stopped. Inside the reservoir is a pump that pumps the nutrient solution into the very bottom of the growbed via the feed pipe.

The most common type of pump to use is an aquarium pump purchased from any pet store or hydroponics supply shop and it is switched on and off at set intervals by a timer, which can be bought quite cheaply from a hardware store, hydro shop or even your local supermarket. There is a second pipe that connects the growbed to the reservoir called the return pipe. The return pipe is set higher in the growbed so that when the nutrient solution reaches a certain level in the growbed it flows back to the reservoir rather than letting it overflow onto the floor.

flood and drain cycle

Lets have a look at the whole flood and drain cycle in more detail so we can understand a little bit better how it all works. What you should bear in mind when you look at the flood and drain cycle is that plant roots need air as well as water and nutrients and optimum growth is achieved when the plant gets all three things in reasonably correct proportions. Experimentation is the key to working out at what intervals the pump should run and it varies depending on the climate the system is operating in. Operating the pump for a duration of 15 minutes every two hours is a good starting point.

Diagram 1 shows the system in the aerating stage. The pump is off and any remaining nutrient solution is draining through the media back into the tank. The plants roots will likely still be moist but air will be present in the growbed. This is the state that the hydroponics system will be in the majority of the time.

Diagram 2 shows the flow of nutrient solution into the growbed when the timer switches the pump on.

Diagram 3 illustrates the flow of nutrient solution from the pump, into the growbed and back into the reservoir through the return pipe. The return pipe protrudes into the growbed and its position determines how much of the growbed will be filled. About 5cm (2″) below the top of the media is a good level to fill the growbed to.

Diagram 4 shows the end of the flooding cycle. The timer has switched the pump off and now the pump is not running the nutrient solution can flow back into the reservoir through the feed pipe and pump. It is important to not put a non-return valve into the feed pipe for this reason. As the solution flows back into the reservoir it draws air into the media and the sytem commences aerating once again. The plant roots and the media will still be quite wet at this point.

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