The Deep Water Culture Hydroponic System

The Deep Water Culture Hydroponic system gets its name from the way that this method, unlike all other hydroponic methods, has the roots of the plants immersed in the water-based nutrient solution all the time. The plants’ root systems aren’t occasionally doused in the solution or allowed to have the nutrient solution flow through them at intervals. Instead, this is full-on immersion for the entirety of the plants’ growing cycle.

The secret is that the nutrient solution is well-oxygenated. Ensuring that these air bubbles provide O2 to the plant is one of the secrets of the DWC system‘s success. Growers can make an oxygen-rich nutrient solution utilising air stones, air pumps and airlines.

The term “deep water” also describes how the method uses a relatively deep reservoir which contains the nutrient solution. The mix and strength of your solution will remain constant and uniform, as opposed to a smaller volume, which will have to be topped up more often, leading to inconsistencies in the strength.

This practice also means mixing the nutrient solution and filling the reservoir once, which will last longer, meaning less maintenance for users of this kind of system.

The nourishment within the nutrient solution exists in three essential parts:

  1. Water. The large volume of the nutrient solution consists mainly of water, and the fact that you’re permanently immersing your plants’ roots means they receive constant nourishment. Your reservoir should be completely opaque so that no light gets in; without light, algae cannot grow, and you don’t want algae in your system. Some bacteria are good, but most are not, so the general rule is to keep everything as free from bacteria as possible.
  2. Nutrients. Growers usually obtain these to add to water at the start and then refill again when necessary. The mix will contain just the right proportions of macronutrients and micronutrients needed for optimum growth and health of your plants. A commercially available product ensures you’ll use a thoroughly tested and optimised mix produced under stringent lab conditions.
  3. Oxygen. Your plants will need plenty of O2 because, without it, they may drown because of their constantly immersed situation. An air stone or pump maintains the oxygen supply, or often both.

The plants’ root systems are constantly submersed in nutrient-rich water with plenty of good, circulating oxygen. This total immersion “culture” is thought to foster such a high yield in plants grown in this way.

Not only should you get a better yield, but your plants should grow faster. Assuming everything else is equal, Deep Water Culture systems will grow plants faster than other hydroponic systems and up to twice as quickly as soil-based gardening methods.

What are the Best Plants to Grow in a DWC System?

Lettuce and herbs will do very well in a Deep Water Culture system. You could also grow tomatoes quickly. The DWC system is quite happy to accommodate large fruits such as squash, and the plant size is not crucial with DWC as with some other types of hydroponic systems.

Environmental Conditions for Deep Water Vulture Systems

Some growers report that it can be challenging to maintain the reservoir at a constant temperature, so you need to monitor this. The temperature should be no higher than 20°C. The O2 levels in the water will begin to drop if the temperature is higher than this. 

But it should be no lower than 16°C either. Below this, there’s a danger that the plants will become confused and think the season has changed, which could lead to the plants’ energies shifting away from growth to flowering, which you won’t want to happen during the growth phase of a plant.

The pH of the nutrient solution needs to be 5.5 to 6.5, but your plants may favour a shift higher or lower depending on the growth stage. During the vegetative phase, they prefer the higher end of the scale, and when flowering, the lower.

You can check the oxygen levels in your nutrient solution with a meter to measure the dissolved O2, and these readings are very precise. Maintaining the proper temperature usually means that the oxygen levels are always optimum. Also, your air pump will need to be constantly running, so a backup battery system or generator is ideal if any outage occurs.

As a matter of environmental control, you should ensure that only the root system of your plants immerse in the nutrient solution. Don’t immerse the stem in the DWC hydroponics system. You’ll want to ensure that, in practice, about 2-3 centimetres of the top of the root system is clear from the nutrient solution. This top part of the roots won’t dry out because of the bubbly nature of the liquid beneath it, and creating this small gap ensures that you don’t immerse the stems.

Water pumps within DWC systems work to speed up the germination and seedling phase of a plant life cycle. Drip lines connect the tank to the plants’ net pots, and the nutrient solution feeding the root system contains more oxygen bubbles.

The advantage here is that with this, you are getting so much more oxygen into the plants’ roots. Plants will tend to grow bigger and faster than without this addition. It also increases the uptake rate of the nutrients by providing more O2, which aids the chemical process of transferring the nutrients to the plants. 

Adding extra oxygen is a deterrent to disease, as the microbes that cause disease will find it challenging to exist in this environment. The rushing action of the pumped nutrient solution will also keep it well mixed so it cannot stagnate.

How to Build The Deep Water Culture Hydroponic System

A Deep Water Culture hydroponic system is straightforward to build. 

Here’s what you’ll need:

You connect your pump to the rubber tubing and the tubing to the air stone. You then put the air stone into the large bucket or reservoir and fill the bucket (as the reservoir) with water, then add the nutrient mix and the pH control pack. Place your cuttings in the pots.

Your plants will start to grow, and when the roots reach the water level, they will begin rapid growth, as the roots will suck as much of the nutrient solution as they need. The roots can continue to remain primarily submerged in the nutrient solution. Then leave your plants to grow.

You’ll find that your plants will grow quickly and healthily in this highly nourishing environment. If you’ve moved from soil to DWC, you may be surprised by how fast this all is. With the Deep Water Culture method, your plants will grow twice as quickly as soil-based methods, so be prepared for that.

The Recirculating Deep Water Culture System

If you want to scale up, you can go to the next level, which is the Recirculating Deep Water Culture system (R-DWC).

If you want to grow many plants, you will not want to have to deal with each bucket and individually adjust the pH levels and calibrate each bucket. Instead, it’s much more efficient to have the main reservoir and use that to feed the nutrients to all the different buckets. The result is the R-DWC system.

The recirculating part is from pumps introduced to the system to boost the supply as it moves around; the nutrient solution becomes rich in O2, which is even better for your plants.

The difference is much more efficient because you only have to control and calibrate the nutrient solution from one source.

Changing your nutrient solution depends on the size of the nutrient solution reservoir, the kind of plants being grown and their growth stage. But the longest you should go without changing your nutrient solution would be about three weeks if you’re using a big enough container as a reservoir.

As mentioned above, you’d want a reservoir capable of holding a large amount of nutrient solution, which is always of uniform strength delivered to your plants. Plants always like this uniformity and are easily thrown off balance if anything in their environment changes suddenly. You also want the reservoir to be large enough so that you don’t have to change it every three or four days.

Advantages of the Deep Water Culture Hydroponic System

DWC systems are popular for many reasons, the primary one being that they’re one of the most straightforward systems.

Advantages of the Deep Water Culture system include:

  • Easy to set up and maintain
  • One of the most manageable hydroponic systems to use
  • Generally considered to produce a better yield
  • It works fast, hence a shorter growth cycle and more frequent harvests;
  • Relatively few moving parts to go wrong;
  • No timers are needed.

Disadvantages of the Deep Water Culture System

Yes, there are disadvantages with the Dep Water Culture system as well.

  • pH levels and nutrient strength (PPM/EC) may not be uniform in smaller DWC systems;
  • You may find maintaining a constant temperature in your reservoir tricky;
  • A power cut will cause your pumps to stop pumping air, causing your plants to drown;
  • You need to change or top up the tank in small systems more often.

The bottom line is that you will have to keep an eye on the temperature of your nutrient solution and watch out for fluctuations in PPM/EC/TDS.

One final word of warning. It’s rare, but you may find that the roots of your plants have developed a disease such as Pythium, a parasitic infection thought to be transferred by fungus gnats.

But if you watch out for these things, then you’ll be rewarded by a harvest which is healthy, plentiful and very fast.