Deep Water Culture (DWC): What Is It And How To Get Started

If you’re new to growing plants hydroponically, terms like Deep Water Culture can sound like they’re straight out of a science-fiction movie. Compared to soil gardening, hydroponics may seem more complex, but it’s really not.

There are many types of hydroponic systems, and many have confusing-sounding names (nutrient film technique, deep water culture, ebb and flow). But that’s why we’re here to break it down.

Let’s take a look at one of the simplest and most popular methods of hydroponic gardening today: Deep Water Culture, or DWC.

If you’re more of a visual learner (like me), check out the video I put together on my YouTube channel below. It gives an overview of how the system works and what you need to get started.

What Is Deep Water Culture (DWC)?

Before we get into the nitty-gritty details, let’s start with a high-level overview of this type of system. In a DWC system, a plant’s roots are suspended in a well-oxygenated solution composed of water and nutrients.

There are three critical parts of this solution:

Oxygen: Because the roots are submerged in water and not soil (which has gaps and holes where air resides), the water needs to be well oxygenated so the plant doesn’t drown. This is accomplished with an air pump and air stone.

Water: Think of this system as if you’re growing in soil and permanently watering your plants. This is one of the reasons growing hydroponically is so beneficial — you never need to “water” again.

Nutrients: Good quality soil contains all the micro and macro nutrients a plant needs to survive and thrive. Because we have no soil, we need to supplement the oxygen-rich water with nutrients so our plants can grow.

This method is called Deep Water Culture for two reasons. First, you typically grow with a reservoir that can hold a decent amount of water. More water means more stability in your nutrient solution, which means less monitoring and maintenance for you.

The second reason is how much of the root mass you submerge in the water. Other methods expose your plant’s root zone to air and drench them in water just a few times a day (ebb and flow systems are a good example). In Deep Water Culture, most of the plant’s root system is submerged 24/7, hence the name.

Benefits of Deep Water Culture

DWC systems are popular for many reasons, the primary one being that they’re among the simplest types of systems to start with. The only system that’s simpler is a wicking system.

Here are a few other benefits of growing in a DWC system:

• Very low maintenance once set up
• Extremely fast growth compared to soil (I’ve grown lettuce to harvest in 30 days instead of 60 in soil)
• Very few moving parts and minimal assembly

Downsides of Deep Water Culture

However, it’s not all sunshine and roses. There are some potential issues with this type of system that can cause problems. Most of these are avoidable if you’re actively maintaining your garden:

• In small systems, pH, water level, and nutrient concentration can fluctuate wildly
• It’s easy to over- or under-calibrate due to the small scale
• If there’s a power outage or pump failure, your roots may “drown” in low-oxygen nutrient solution
• It can be difficult to maintain a consistent water temperature

Building a Deep Water Culture System

Traditional DWCs are the easiest to build. Here’s a list of the parts you’ll need to set up your first system:

• 5-gallon bucket
• Air pump
• Air stone
• Airline tubing
• Net pots
• Growing media
• Hydroponic nutrients
• pH control kit
• PPM meter

The method is simple: connect the pump to the tubing, the tubing to the air stone, and place the air stone in the bucket. Fill the bucket with water, adjust the pH, add your nutrients, and start your seeds.

Once your plants begin to germinate and the roots start to reach the water, you’ll see an explosion of growth. Instead of spending energy growing roots to search for pockets of water in soil, your plants can simply absorb as much water and nutrients as they need right away.

If the water is properly oxygenated, there’s no reason your plant’s roots can’t remain submerged in the water (hence the name) for the entire life cycle of the plant!

Because of the highly oxygenated and nutrient-rich solution, plants grown in a traditional DWC system can be harvested up to twice as fast as soil-grown plants. I’ve personally harvested a head of lettuce in just 30 days from germination.

The fastest I’ve ever grown lettuce in soil is 60 days.

Recirculating DWC

The traditional method is amazing for beginners, but what if you want to scale your system to the next level? Most people move to an RDWC, or Recirculating Deep Water Culture system, when they’re ready to upgrade their garden.

If you’re looking to grow at scale, the last thing you want is 10 individual buckets, each requiring its own calibration and adjustment. If you’re growing the same plant across 10 different buckets, doesn’t it make more sense to have one main reservoir and feed that nutrient solution to all 10 buckets?

If you said yes, you just invented the RDWC system!

You might be wondering how oxygenation works when you have multiple buckets chained together. Just as it would be inefficient to have separate nutrient solutions for each bucket, it’s also inefficient to run an air stone system for each one.

This is where the “recirculating” part of the name comes into play. As water moves from bucket to bucket, it’s shuttled around via spray nozzles that oxygenate the water.

The beauty of this modification to the classic DWC system is that you only need to calibrate, oxygenate, and top up water from one central location, and it gets fed out to all buckets immediately. The best analogy here is the power grid: we don’t run our own generators in our homes. Power is generated at centralized locations and then sent out through the grid to our houses.

Bubbleponics

Although many people don’t consider Bubbleponics to be all that different from traditional DWC, I personally think it has a few advantages and is important enough to talk about. Despite its silly name, the adaptation Bubbleponics makes is simple.

Instead of waiting for your plants to germinate and for the roots to reach the top of the water in your reservoir, Bubbleponics speeds up the process by top-feeding the nutrient solution to your plants during the first few weeks.

All that’s happening here is the addition of a water pump to the system, with drip lines running up out of the tank to the net pots your plants are sitting in. Simple, but very effective in accelerating the germination and seedling phase of a plant’s life cycle.

Maintaining a Deep Water Culture System

Once your system is ready to use, you may have a few questions on how best to use it. Here, we break down common questions and answers.

Should I Use a Singular or Modular System?

If you’re just starting out, go with a single reservoir setup. You can build them yourself or buy one of the many on the market. A modular DWC system is better for growers who know exactly what they want to grow and how much they want to grow. Start small and scale up as you get more experience.

Should My Reservoir Be Sterile?

This is not a yes or no question. Some hydroponic gardeners want to keep their reservoir sterile. This means they won’t have any of the biological contaminants that might plague a hydroponic garden, like algae. But at the same time, they won’t be able to take advantage of beneficial bacteria. If you do decide to add beneficial biology to your reservoir, just be aware that it comes with the risk of having not-so-beneficial biological organisms tag along for the ride.

What Should My pH Be?

Just because you’re growing in a deep water culture system doesn’t mean you need to adjust your pH and PPM/EC drastically. The standard range that most plants prefer (pH 5.5–6.5) is perfectly fine. However, you’ll want to customize and monitor this based on the stage of growth your plants are in. When they’re in the vegetative stage, aim for the higher end of that range; when they’re flowering, stick to the lower end.

As for your PPM/EC, don’t blindly follow the feeding schedule on the back of your hydroponic nutrients. These recommendations are typically higher than necessary. Try cutting the amount in half and observing how your plants respond. You can always adjust upward quickly, but adjusting downward is more difficult—your plants may have already suffered from nutrient burn.

What Should the Temperature of My Reservoir Be?

This is one of the downsides of deep water culture: it can be hard to control the temperature of your reservoir. Aim for no higher than 68°F (20°C). If you get much higher, the oxygen level in your water starts to drop (even if you’re oxygenating with an air pump and air stone).

Also try to keep it above 60°F (16°C). If it goes any lower, your plants think that they’re moving into a new season, typically fall or winter. This means they’ll start to divert more energy towards flowering, which you may not want.

When Should I Change my Nutrient Solution?

The longest you should wait before changing out your solution is three weeks, but this is just a general case. It depends on:

• ​The type of plants you’re growing
• The stage of growth they’re in
• The size of your reservoir

If you want to avoid a complete change, you can try to add water with some nutrient solution mixed in to get the right balance again, but this is difficult to do. A complete change may be the better route.

How Do I Know How Much Oxygen is in My Nutrient Solution?

Dissolved oxygen meters are available for purchase, but they’re pricey and may be overkill unless you need extreme precision. I wouldn’t recommend buying a lower-end one either, as they’re not very reliable. The best way to “monitor” your dissolved oxygen levels is to focus on maintaining the conditions that keep those levels high: keep the solution at the right temperature and ensure your air pump is running consistently.

How Much of the Roots Should Be Submerged?

First of all, make sure that only the root matter is submerged in your nutrient solution (not the stem, and certainly not any vegetation). You also don’t want to completely submerge the roots. I personally keep about 1 to 1.5 inches of root above the water line. The bubbles from the air stone will usually pop and splash water onto the exposed roots, so you don’t have to worry about them drying out.

Frequently Asked Questions