Growing Cannabis with Deep Water Culture (DWC)

For those ready to break the routine of growing organic Cannabis, deep water culture (DWC) is an advanced growing method for large yields using a soilless growing medium. For certain growers, this method may be music to their ears. 

In this article, we break down all you need to know about DWC, including how it works, the pros and cons, and how to set up and maintain a system. We’ll also provide an understanding of pH and EC and our top tips when growing cannabis with deep water culture.

What is DWC, and how does it work?

Basically, Deep Water Culture is a nontraditional way of growing cannabis. It requires a 4 – 5 gallon / 15-20 liter bucket, an inert growing medium, and a nutrient solution. The plant’s roots stay permanently submerged in the nutrient solution. Dissolved oxygen produced using an electric air pump and air stone creates the ideal growing environment for roots. 

Because you can choose the nutrient concentration over time, your cannabis plants will grow much quicker during the vegetative stage using a DWC system and produce heavy yields once flowered. Depending on the cultivar, the final size of a plant flowered in DWC can be between 75-150 cm tall.

The pros and cons of Deep Water Culture for cannabis

Out of all the hydroponic systems, it is fair to say that deep water culture hydroponics is the most complex. It also has the highest risk-to-reward factor. There are both pros and cons to growing cannabis using DWC, which I’ll cover below. 

The pros of DWC

• Faster growth – When it comes to turnaround time and return on investment, faster growth during the vegetative stage (18/6 light cycle) lets a grower flower their plants and harvest quicker than a traditional 6-8 week growth period. This means more harvests per year and, ultimately, more return on investment.

• Massive root mass – When roots are left submerged in an oxygen-rich environment, the ability of a cannabis plant to produce a larger root zone is easy. The bigger the roots, the more hydroponic nutrient solution the plant can absorb, producing big, dense, and resinous buds.
• Access to nutrients 24 hours a day – One of the best things about DWC is that you can’t overwater your plants, thanks to the gentle jacuzzi of bubbles they’re chillin’ in. Combined with access to primary nutrients and trace minerals, it’s no wonder DWC stands out from the rest when talking about yield potential.
• Increased yields – Many frustrated organic growers reach their turning point when constantly producing small-yielding crops. It is possible to increase yields by 200-300% when growing fruits and vegetables with hydroponic methods, and the same certainly applies to cannabis buds. 
• Homemade systems – Designing custom DWC systems is easy and won’t break the bank. You only need a bucket with a lid, net pot, coco jiffy, or a piece of rockwool to start the seeds inside and some hydroton clay balls. You can pick up a fish-tank-quality air pump and air stones at your local pet store or garden supply store. 

The cons of DWC

Now that we have covered all the benefits of jumping ship to DWC, it is time to discuss all the downsides of this (potentially) expensive indoor hobby. 

• Power cuts and air pump failure – All hydroponic systems require either a water pump or an air pump, which all have moving parts and require an electric source for power. A failed air pump or long-term power cut can cause devastating losses to mature DWC plants. Those who do not have a backup pump will have a limited amount of time to fix the problem.
• Noisy and rattling air pumps – When discretion and stealth are important for an indoor grower, coping with the noise created by whirring exhaust fans, oscillating fans, and grow lights can be a headache, especially when you live in a residential building or close to a neighbor. Be prepared for a loud, floor-shaking humming noise when running your grow. 
• Root rot – This is often the number one cause of all major problems when growing with deep water culture. Sometimes, the water temperature or lack of oxygen can cause plant roots to turn from a bright white to a dark yellow and soggy texture overnight. The solution to root rot is to bathe the roots in 3-10% hydrogen peroxide, depending on the needs of the plants. 
• Water temperature – You’ll need a heater to keep the water temperature consistently 18-20 degrees Celsius / 65 – 68 degrees Fahrenheit. You must be able to increase or lower the temperature as needed, as consistency is key when using deep water culture systems.
• Costs of nutrients and manual labor – Deep water culture can become an expensive game, as filling up 4 – 5 gallons (15-20 liters) frequently with several different nutrients is costly. This is especially true when an issue necessitates changing and refilling the reservoir. Be prepared for frequent reservoir changes and invest in plenty of nutrients, as running short is not really an option.

How to set up a deep water culture system

How to maintain systems and care for your cannabis plants using a DWC setup

Once you have filled your buckets with a nutrient solution and turned the air pumps on, you are ready to start your career as a hydroponic grower. However, there are a few variables to consider when looking after the systems and maintaining quality control. 

• Water quality – The quality of your water source will determine how many nutrients you can give your plants. Generally, reverse osmosis (R/O) water is the best starting point for a first-time hydroponic grower. R/O water has a minimal EC, allowing the plants to absorb more nutrients. Using soft water over hard water is always the best bet when using deep water culture systems. 

• Air pump – Air pumps left on 24 hours a day for months may begin to fail and dip in performance. You should expect this with any electric equipment composed of moving parts. Buying a new air pump every few harvests is always a good idea, and backup air pumps are a must!
• Temperature of the nutrient solution – For the roots of a cannabis plant to take in the primary and trace elements available, there needs to be a balance between the pH of the solution, EC level, and water temperature. A heater set to 64.5 degrees Fahrenheit (18 ℃) or a water chiller will be the best options to maintain consistency. 

A freshwater supply for healthy roots

Because the roots of your cannabis plants secrete toxins over time, it’s important to replace the water in your reservoir often. These toxins cause the water’s pH to drift – either increasing or decreasing. This is also how plants can absorb precisely what nutrients they need. Changing the reservoir with clean water is essential, especially during the flowering stage.

Healthy roots growing in the ideal environment will be similar to white noodles, with fishbone characteristics. The roots will be compact and well spread out and, when taken out of the water during the reservoir change, have a well-developed and heavy mass.

Important notes:

• Plants release toxins from their roots and pollute the water.
• There will be a gradual increase in the strength of the nutrient solution over time.
• Roots should be shiny white in appearance with fishbone root characteristics.

Understanding pH and electric conductivity (E.C)

In the way that growing organic cannabis needs a nutrient solution in a certain pH range, the same applies to deep water culture. The term pH means Potential Hydrogen. It determines if the water is acidic, alkaline, or neutral. Hydroponic systems will produce the best results when the provided nutrient solution has a pH level of 5.5 – 6.5. You can easily adjust the pH of a nutrient solution using drops of pH up or pH down.

Electric conductivity refers to how much salt is present within a water source, determining how much conductivity the solution will have. As plants mature, their ability to uptake a higher EC increases, letting them grow fast and produce abundant buds. 

The best way for a first-time grower to accurately check their pH or EC is by using digital pens. Some pens can check both depending on their settings. These $15-$30 devices will produce a digital reading for you and are a lifesaver for all types of hydroponic systems. 

How does DWC differ from other hydroponic methods?

When it comes to the various hydroponic systems, DWC will be the highest-yielding. However, it is undoubtedly the most complex and expensive due to the high volume of nutrients. 

From a skill level, it can be the least forgiving hydroponic system, requires vigilance, and the risk-to-reward factor is much higher than other systems. Below are other hydroponic systems to consider if you are new to hydroponics and wish to work your way up the ladder in terms of skill and experience. 

1. Flood and drain systems – Not as popular as they once were in the old days, flood and drain systems require a table and reservoir connected to a pump. Nutrient solution rises and floods the rockwool cubes or hydroton for a short period of time. Flood and drain and Sea of Green setups go hand in hand and were very popular once upon a time.
2. Dripper systems – Described as the entry-level point for those jumping from organic to hydroponics, dripper systems that feed the plants for 15 minutes per time are very practical to use and eliminate the thought of hand watering an entire room or warehouse of cannabis plants. 
3. Nutrient film technique – NFT tables allow the roots of your cannabis plant to sit on a table and access a fine film of nutrient solution. NFT also helps plants become enormous in a short time. Growing plants using nutrient film technique systems requires a short vegetative time of 7–10 days at the maximum before flowering under a 12/12 light cycle.
4. Aeroponics – Originally the brainchild of NASA scientists who wanted to grow vegetables in space, aeroponic systems are designed almost identical to deep water culture buckets. However, with aeroponics, you use a spray nozzle to wet the roots with a nutrient solution. There are two types of aeroponic systems- low pressure and high pressure – both require different nozzle sizes and water pressure levels. 
5. Aquaponics – You will most likely never try aquaponics or see an aquaponics garden growing cannabis. Aquaponics involves using living fish and a specific food source. You then allow the roots to submerge inside the tank. Imagine DWC on a massive scale outdoors with carp fish, and then you will get the idea.
6. Reverse Deep Water Culture (RWDC) – Once you have mastered DWC, the next level is using an RWDC system, housing many buckets together simultaneously. This system acts as a network of connecting buckets that uses one main reservoir output. RWDC requires an advanced skill level and plumbing work when setting up.

Get your hydrophonic seeds

Flushing cannabis plants using deep water culture

When growing cannabis using an organic growing medium, it is necessary to flush the roots with plain water for at least 14 days. You flush cannabis plants in the first place to promote the use of internal nutrient reserves and allow the undissolved accumulated salts to break down and wash away. 

Flushing cannabis plants with deep water culture systems only requires one week of flushing programs, usually performed with reverse osmosis water or an enzyme solution. A well-flushed plant grown in DWC should have a smooth, flavorsome, and mouth-watering taste with a soft and gray ash quality. The joints should burn uniformly and not require constant lighting or cause unwanted coughing fits when smoking.

My top tips for growing cannabis in deep water culture

Top Tip #1 – Having a backup air pump is one of the best pieces of advice I can give you. There is nothing worse than the heart attack feeling of hearing your room silent and the pumps not working. Have at least one extra pump in the event of an emergency.

Top Tip #2 – Dissolved oxygen increases the pH of water, so keep this in mind when supplying excessive amounts of air. Find an air pump that provides the ideal amount of oxygen without causing the pH to drift too much. 

Top Tip #3 – When making a nutrient solution, I recommend adding your nutrients first, then adjusting the pH level of the nutrients’ solution afterward. Doing this can save you from performing the task of adding pH up or down twice every time. 

My final thoughts on DWC

Making the jump to hydroponics after decades of growing can be both a breath of fresh air and a new challenge and discipline to master. I recommend starting with a dripper system. Over time, work up your skill level and experience to the point that you are more than comfortable with the fast-paced and expensive world that comes with deep water culture. 

I  hope this article will help you better grasp DWC and allow you to take your yields to the next level! For more information on growing and harvesting, check out Robert Bergman’s Grow Bible!