The Recirculating Deep Water Culture System (RDWC) Guide

Deep Water Culture (DWC hydroponics) is a hydroponic gardening method used to cultivate plants indoors, outdoors, in greenhouse kits, or in grow tent systems.

DWC is a soilless hydroponic method where plant roots grow suspended in an oxygen-rich hydroponic nutrient solution containing water and essential nutrients.

A Recirculating Deep Water Culture (RDWC) system enhances DWC hydroponics by adding a hydroponic pump that continuously circulates and mixes the hydroponic nutrients, and large diameter piping that connects the grow sites to a common reservoir. This ensures even and optimal distribution and continuous mixing of the nutrient solution flowing to each bucket, resulting in healthier plants and higher yields.

What is an RDWC system?

In a Recirculating Deep Water Culture hydroponic system, also known as an RDWC and recirculating DWC hydroponic system, the roots of the plants are submerged in an oxygen-rich nutrient solution 24/7.

The plants are grown in net pots suspended from the bucket lids and contain suitable growing media such as clay pebbles. The clay pebbles provide support for the plant as it grows, as well as absorb the nutrient solution for the plant roots.

As the plant grows, the roots descend into the nutrient and oxygen-rich water solution. The nutrient solution is actively circulated via a water pump through the buckets connected by pipe to the main reservoir, maintaining an even water level across all buckets.

The hydroponic nutrient solution only needs to be added to the central hydroponic reservoir tank, and all plants receive the recirculated, oxygenated nutrient solution continuously.

How does a recirculating DWC hydroponic system work?

Plants need light, water, nutrients, and oxygen for optimal growth.

Oxygen:

The amount of oxygen the plant receives is a major factor in DWC and RDWC systems and is what makes this technique successful.
Since the plant roots are in water constantly, it is important to use quality air stones and an air pump to oxygenate the water and nutrient solution.
The airstone hydroponics create tiny bubbles increasing the dissolved oxygen content in the nutrient solution, which the plants absorb through their roots. This is a critical factor in healthy plant cultivation and root hydroponics for growth.

Water:

In an RDWC Hydroponic System water is conserved as it recirculates through the system.
The plant roots are suspended constantly in the nutrient solution and receive exactly what they need.
Warm water is less capable of holding as much oxygen as cool water; therefore, it is important to ensure that the water temperature is maintained below 80°F.
Experts agree that the best water temperature for hydroponics is between 65°F and 80°F. This temperature range enables plants to thrive and provides an ideal setting for healthy roots and oxygenated nutrient absorption.

Nutrients:

Soil contains essential nutrients to help plants grow and thrive. With soilless hydroponic methods such as RDWC and DWC, plants require a nutrient-infused water solution that enables them to grow and thrive in a soilless environment.
Three nutrients that are essential to plants are nitrogen, phosphorus, and potassium, the N-P-K listed on all fertilizers.
In addition to these three nutrients, plants also need calcium, magnesium, sulfur, and other elements. Different plants require different levels of these nutrients, depending on their growth phase. Hydroponic nutrient solution for vegetables is different than hydroponic nutrients for weed growing. Check out our blog about mixing nutrients for our hydroponic nutrient solution recipe.
A reservoir is filled with the nutrient-water solution and is circulated via the hydroponic pump through the connected pipe in an RDWC system.

How do you use RDWC?

RDWC is great for growing many different crops. Hydroponic weed growing, tomatoes peppers, cucumbers, and other vining crops are easy to grow with this water culture method.

A hydroponic reservoir is connected via pipes to a series of buckets. Plants are grown in net pots suspended from the bucket lids, containing hydroponic growing medium such as clay pebbles.

Air stones and an air pump oxygenate the nutrient solution. The oxygenated nutrient solution constantly circulates around the system. The hydroponic nutrient solution level should be maintained at the correct depth. Typically, this is touching the bottom of the net pot.

The pump creates a water current through the buckets to deliver vital nutrients to the plant roots, optimizing plant growth and root health which results in higher yields.

It is important that the pH and nutrient levels are well maintained to the levels required for the type of plants being grown and phase of growth. For example, small seedlings should have a lower nutrient strength than adult plants. The pH determines the amount of nutrient uptake in the plants. Typical pH levels are 5.7 – 6.6.

Benefits of A RDWC System

Water conservation as water is recirculated and recycled
The nutrient and oxygen-rich water solution constantly recirculates to provide plants with a continuous supply of nutrients
Plants grow faster and healthier than in soil, with higher yields
Lower maintenance than most other systems; it requires monitoring and topping off the main reservoir as needed, and changing water periodically

Which is better, DWC or RDWC?

When planning your DWC or RDWC set up there are many factors to consider.

How much monitoring do you want to do yourself?
Do you want to check and fill each bucket as needed, sometimes daily?
Would you rather use a reservoir, and mix and refill your nutrient solution weekly?
Do you require more precision in the amount of nutrient solution each plant receives?
How much space do you have?

Artisun Technology offers various DWC system configurations from basic, to more elaborate setups. Here is a brief explanation of some of the different types of DWC.

Individual Unconnected Buckets without a Central Reservoir

For systems without a central reservoir, you need to manually monitor the water and nutrient level and top off the solution in each bucket as it is consumed by the plant. Air stones are placed in each bucket and connected to a central air pump. These are standalone buckets since they do not share a water supply, but the air pump is centralized. You can have one, or many buckets.

Buckets Connected to a Central Reservoir

A central reservoir is filled with water and nutrients. Air stones are placed in each bucket and connected to a central air pump. As the plants consume the water and nutrient solution, the solution across all the connected buckets is drawn from the reservoir. The solution only needs to be added to the central reservoir.

Recirculating System

This is the same as the above system, but here water is actively circulated via a pump through the connected buckets from the reservoir. The solution only needs to be added to the central reservoir. The pump ensures even and optimal distribution of oxygenated nutrient solution to each bucket.

Both DWC and RDWC methods enable the roots unlimited access to nutrients and oxygen, which optimizes nutrient intake, grows bigger and healthier and roots and plants, faster and with greater yields.

RDWC vs Dutch bucket

A Dutch Bucket Hydroponic system is typically arranged in rows with one irrigation supply pipe feeding drippers from above and one drainage line circulating back to the main reservoir from below.

The pump in the reservoir sends water flowing down the line through the drippers. Later the drainage line returns the excess water solution from all buckets back to the reservoir and the water is recycled.

Siphon elbows in the Dutch buckets enable good drainage for plant roots. Easily joined together, these systems can be scaled to any size.

Ideal for growing vining plants such as peppers, tomatoes and eggplants, a Dutch bucket system is a great choice for greenhouses and patios and is a simple Hydroponic method for beginners.

In DWC Deep Water Culture Hydroponic systems, plant roots grow suspended in a well oxygenated nutrient and water solution. “Deep” means that the roots must be submerged deep in the water.

RDWC Recirculating Deep Water Culture takes traditional DWC method to another level by continuously recirculating and mixing nutrients and oxygen and creating a steady flow of water while maintaining a constant level throughout the system.

Is RDWC Pre-Made Kit or DIY Setup Better?

Should I purchase a pre-made RDWC kit or build my own DIY Hydroponic system? That depends on many factors. How handy are you? How much time do you have to invest in building a system from scratch? How quickly do you want to start growing?

Pre-Made RDWC Kit Recommendations

Artisun Technology’s RDWC System provides an out-of-the-box complete system with detailed setup instructions that gets you set-up and growing in no time with proven results and a quality grow. NO cutting, drilling, gluing or additional tools required.

DIY RDWC Recommendation

If you are handy and enjoy designing and building, Artisun Technology can also provide you with some of the growing equipment such as square buckets, hydroponic tubing and more, to build a DIY hydroponic indoor RDWC system.

What are the materials used?

Buckets / grow sites
Reservoir
Net pots with Lids
Air tubing
Bulkhead fittings and connectors
PVC pipe or vinyl tubing
Air stones
Air pump
Water pump

We always suggest that before building your system you wash components in warm soapy water and rinse properly.

After building either a pre-made RDWC kit or a DIY, fill the system up with water slowly and check for leaks, ensuring all fittings have been tightened before starting your garden.

Start the process by adding a little water at a time. After testing, empty the water completely and fill it up again before adding the plants.

Common Questions About RDWC Systems

Which plants grow in RDWC?

Many varieties of plants can be grown using the RDWC system. Tomatoes, peppers and cannabis are just some the many types that will thrive in a Recirculating DWC system.

Do you need an air pump for RDWC?

An RDWC hydroponic system requires an air pump and at least one air stone. Artisun Technology provides one air stone per bucket / grow site to enable greater oxygenation.

How many GPH do you need for RDWC?

For Artisun Technology RDWC systems with 4 – 8 buckets, we recommend a 250 – 400 GPH water pump.

How do I change the water in my RDWC?

Artisun Technology provides a separate drain pump with bottom entry inlet fitting and tubing in our RDWC systems. When a water change is required, this pump can be lowered into the reservoir in order to pump water out to a sink, drain or bucket that can be emptied. Refill reservoir with fresh nutrient water solution.

How often do you change water in RDWC?

Completely changing the reservoir water every 7 to 10 days is preferable. You can top off the nutrient solution in the reservoir as needed.

What do you need for RDWC system?

These are most of the items needed for a Recirculating Deep Water Culture system: Buckets / grow sites, Bucket lids with hole and net pots, a main reservoir with lid, an air pump, an air stone per grow site, air tubing, piping, adjustable water level control spout, clay pebbles, recirculating pump, and drain pump

Can roots grow through Hydroton?

Hydroton is one brand of clay pebbles and is a popular growing medium used in Hydroponic gardening. It comes with several benefits, such as reduced water consumption, and it helps provide support for growing plants. It is an environmentally friendly, reusable, loose medium that helps to separate root balls from the media that surrounds them which makes it easier to transplant and pull plants out after harvest.

Can you overwater in DWC?

Overwatering in a Hydroponics DWC and RDWC system is not an issue provided that pH, nutrient, water oxygenation, and water temperature are maintained. Since the roots are constantly suspended in water it is very important that sufficient oxygen is provided to the water using quality airstones and air pump.

How often and when should I flush my Hydroponic System?

Draining and changing the reservoir water solution every 7 to 10 days is recommended. It is also important to note that sometimes root balls may grow too large and can obstruct pipes which could cause a bucket to overflow. Plants should be checked periodically to ensure this does not happen.