These RDWC grow tips will help maximize cropping results and provide all the benefits that RDWC (recirculating deep water culture) hydroponics growing systems offer.

Getting the Most from Your RDWC Set Up

Running an advanced RDWC hydroponics system such as the Under Current requires additional accessories to maximize the potential of a garden. Ensuring your garden has the ideal conditions it needs to produce can be made easier when following these well-developed and proven RDWC grow tips. In our latest Growers Blog, you will find out how best to utilize these accessories to work for your garden.


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CCH2O Under Current RDWC hydroponics system how it works

Water Chiller

Utilizing a water chiller when running the Under Current system is crucial to the success of your garden. The RDWC technology the Under Current system employs submerges much of the plants roots structure within the nutrient solution. The nutrient solution becomes the plants media. This fact requires ideal root zone conditions to be provided to ensure plants stay healthy and produce to their maximum potential. Ideal root zone conditions begin with optimal temperatures (65°-70°). Employing a water chiller in your garden is the most effective way of providing the correct root zone temperatures your plants require.
The highest levels of dissolved oxygen are only accessible when utilizing cool solution temperatures. As solution temperatures rise, its ability to hold dissolved oxygen decreases. This warm, low oxygen environment also provides the ideal conditions for dangerous pathogens, such as root rot (Pythium), to take hold of your garden.

Water chillers can be directly integrated into the Under Current systems circulation process. As nutrient solution circulates throughout the system, it passes through the water chiller, where it is cooled by coils to preset temperatures. The cooled solution then flows into the epicenter and back into the recirculation process.

Chiller Sizing

When sizing a water chiller for your Under Current system, start by determining your total system volume – for 8-gallon systems assume 6.6 gallons per module and for 13-gallon systems assume 11 gallons per module. As a rule, it is recommended to choose a water chiller that can handle an additional 20% capacity of your total system volume to make up for any performance loss. Much like all grow room equipment, water chillers create heat. For this reason, it is also recommended to place water chillers outside the grow room, or to exhaust the heat created outside of the grow room.

Meter: ppm/EC, temperature, & pH

Growing in an advanced system such as the Under Current requires very specific inputs. The high levels of dissolved oxygen the Under Current system provides supercharges plant nutrient uptake. As a result, fewer nutrient inputs are required. For this reason, solution ppm/EC, temperature, and pH must be precisely controlled.

Meters offer this precise measurement control. They are an invaluable piece of equipment that can assist growers in monitoring their plant’s environment. Utilizing a meter will also assist in documenting grow room conditions and making any necessary adjustments to improve plant performance. The Under Current system was designed to be used in conjunction with meters and automation equipment, taking much of the manual labor associated with media gardens out of the equation. Metering systems are the first step to less labor and higher yields.

Top-off Reservoir

Top-off reservoirs are essential in ensuring the Under Current system performs correctly for your garden. Much like the above-mentioned equipment, the top-off reservoir performs the very important function of ensuring the correct conditions are being provided to the plant’s roots zone.

The top-off reservoir is a separate container that stores nutrient solution and freshwater for your Under Current system. It is directly connected to the epicenter and its flow rates are controlled by the epicenter float valve. As plants uptake nutrient solution, the top-off reservoir works with the float valve to replace this lost solution, maintaining set solution levels.

Top-off reservoirs maintain accurate and essential solution levels throughout the course of the growing cycle, ensuring plants are never left without the solution levels they require. Solution level fluctuations will cause undue stress, poor plant performance, and/or even complete crop loss. Another benefit of top-off reservoirs is that they also allow for easy nutrient solution change-outs, reducing the labor required in maintaining the Under Current system.

Top-off Reservoir Sizing

When sizing for a top-off reservoir, ensure the reservoir size is equal to the total system volume, plus 10% extra.

If the total system volume is 100 gallons, the top-off reservoir should be 110 gallons minimum.

Choose a top-off reservoir that works for your growing space. The Aquifer brand of premium reservoirs work great with the Under Current systems and come in multiple sizes to fit your growing space.

Connect the top-off reservoir to the epicenter through the float valve and set it to desired solution level. This set level will automatically be maintained. Ensure the top-off reservoir is placed on a flat, stable surface to prevent any potential for tipping or spilling. For best results, place the top-off reservoir in an elevated position above the system solution level, to aid in draining and gravity-fed top-off.

Filling, mixing and pH balancing your nutrient solution can all be done in the top-off reservoir. We recommend the top-off reservoir solution strength be set one week ahead of the Cultured Solutions Feeding Schedule. As the nutrient solution is used up, the next week’s solution is slowly added to the Under Current system. This gives your plants the smoothest transition possible to changes in nutrient strength and/or additives.

In addition, the top-off reservoir can be used as freshwater storage when used with metering and dosing equipment for full automation of the Under Current system.

Suggested Accessories

Although not required like the above-mentioned equipment, there are several accessories that could be of use to those running the Under Current system to maximize their garden’s potential.

Module Cage

Whether growing trees or using sea-of-green techniques, the CCH2O Module Cage offers sturdy support and excellent anchor points for training plants as they enter their flowering stages. The modular design of the CCH2O Module Cages allows it to be used with established plants then easily broken down when harvest time comes around. The CCH2O Module Cage fits both the 8 and 13-gallon MultiMod Growth Modules. A well-supported plant will yield heavier, have more consistency in harvest quality, and be prone to fewer problems. Heavy crop loads without sufficient support can snap limbs and create situations where airflow through the canopy is restricted or impeded.


The CCH2O UC Parkas are a great way of enhancing the chilling efficiency of water chillers. Made of 96% reflective material the UC Parkas are capable of reflecting heat, while also retaining cool nutrient solution temperatures. Simply insert onto the Under Current system growth modules and leave for the entirety of the growing cycle. The CCH2O UC Parkas are available in sizes to fit the MultiMod 8 and 13-gallon growth modules.


Consistent Aeration

Aeration levels have a direct relationship with growth rates and how efficiently roots take up water and nutrients. When RDWC systems operate with optimal aeration levels, nutrients can be applied at ¼ strength versus conventional growing methods for outstanding results. Until recently, growers have had to guess how much aeration is being delivered to hydroponic reservoirs and root systems, making replicable results more challenging to achieve.

The Air Flow Regulator from CCH2O comes standard with all complete UC Systems and is also available as an accessory for growers who want to manage aeration levels in their water tanks, systems, and hydroponic reservoirs. An Air Flow Regulator gives growers the means to consistently dial-in aeration levels to known, measurable, and repeatable values and works in conjunction with a wide variety of air pumps and regenerative blowers.


Avoiding Plant Shock & Stalls

Changing or adjusting nutrient solutions is necessary for RDWC systems. If not performed by an automatic dosing system or top-off reservoir, adding to the nutrient solution that the plants are actively growing in is necessary.
An abrupt change to the composition of the nutrient solution surrounding bare plant roots can shock plants, stalling growth and development. In severe instances, it potentially damages sensitive healthy roots.
Nutrients, additives, and pH adjusters should be added back to the system very gradually and slowly, especially when supplied in highly concentrated forms. It’s not practical for growers to hand-pour concentrates into the system very slowly, one component at a time. That’s why CCH2O offers the Add-Back Kit. The Add-Back Kit requires no electricity and uses the flow of nutrient solution at the EpiCenter to gradually siphon up nutrient concentrates and slowly dilute them into the flow of nutrient solution crops are growing in. The rate of additions is fully adjustable, and when not in use remains attached to the system while operating.

CCH2O ADD BACK KIT hydroponics Venturi Driven Fertigation

Utilizing the above required accessories and following our RDWC grow tips in your garden will ensure the smooth operation of the Under Current system. These important accessories support the operational functions of the Under Current system, while also aiding growers. When correctly utilized these accessories will work with the Under Current system to have you on your best harvest yet!