Solution level when ¼ inch below the Planting Deck .
Difference of Operating Volume and liquid left when drained to the top of the bulkhead nut.
Raised portion of the net pot designed to seat the basal stem of a rooted clone or rockwool cube.
Plant-free bucket for circulation control, volume, temperature control, EC, and pH.
Continuous addition of fresh RO water via pressured manifold or reservoir.
The gentle and gradual increase of EC over time.
Reducing EC by letting plants consume nutrients without replenishing; maintain Top Off.
Connected to an air pump/ blower. Distributes air to all grow sites.
Line returning solution to the control bucket for recirculation.
RDWC OVERVIEW
What is RDWC?
Recirculating Deep Water Culture (RDWC) is a hydroponic growing system where plant roots are submerged in a nutrient-rich, oxygenated water solution. The system consists of multiple plant sites connected to a central reservoir (control bucket). The water cycles continuously through the system, returning to the control bucket, ensuring consistent and optimal EC, pH, and temperature for healthy plant growth.
Recirculating Line
Air Manifold
Recirculating Pump
Why RDWC?
Manifold Pump/Blower
Rear Manifolds
NOTE: Place larger clones at the back due to
Front Manifold
Front Manifold
Air Stone
Control bucket
Vigorous plant growth with lush foliage. ROBUST GROWTH NUTRIENT STABILITY OXYGENATION CONTROL STRONG ROOTS
Minimal to no nutrient deficiencies or leaf discoloration.
Accurate ORP, dissolved oxygen, and active bubbling.
Strong root development and white, healthy roots.
PREDICTABLE PH
If pH fluctuates outside of the safe zone, problems can occur. pH should be monitored and strictly maintained.
RDWC WATER IMPORTANCE
Water quality is crucial in RDWC systems for healthy plant growth. Reverse osmosis (RO) water removes impurities like chlorine, heavy metals, and pathogens, ensuring a clean baseline for precise nutrient control. Maintaining healthy water prevents harmful buildup, supports oxygenation, and promotes a healthy root environment, leading to vigorous growth and maximum yield.
ANAEROBIC
Anaerobic conditions occur with reduced ORP levels in the water, leading to the growth of harmful pathogens that can cause root rot and other issues.
Maintaining proper ORP levels keeps water clean and encourages optimal root health and plant growth.
ORP SHOCK
High ORP levels in RDWC can cause shock to the root system. This is caused by a highly oxidized environment that impacts the root’s ability to exchange nutrients.
ORP SHOCK ZONE
ANAEROBIC ZONE
Putrid
Shot of Cleanse during addback
ORP fluctuation over time ORP
Athena ® Cleanse
Initial Mix: 4
Changeouts: 4
NOTE: Young plants do not eat/drink at the same rate of established plants. The amount of Cleanse added to the system should gently increase over the weeks to account for new RO water being added to the system. Cleanse Control Bucket
Athena ® Cleanse is okay to pour into the control bucket in increments of 500 mL or less and can be added to the system with the nutrient addback or by itself.
Athena ® Cleanse
Concentration & Contact Time
ORP SHOCK
WARNING: HYPOCHLOROUS ACID IS SAFE AND NON-DAMAGING TO PLANT TISSUE. HOWEVER, OVERUSE IN A RDWC SYSTEM CAN CREATE A HIGHLY OXIDIZED ENVIRONMENT THAT THAT REDUCES NUTRIENT UPTAKE. RDWC SYSTEMS REQUIRE MUCH LOWER ORP LEVELS THAN OTHER GROWING METHODS DUE TO THE EXTENDED CONTACT TIME AND THE VOLUME OF SUBSTRATE. ORP SHOCK APPEARS AS A NUTRIENT DEFICIENCY--YELLOWING OR DRY, CRUSTY FOLIAGE.
Athena ® Cleanse For Clean Systems
Athena ® Cleanse raises the Oxidation Reduction Potential (ORP) of water, increasing its ability to oxidize and reduce substances like mineral scale and organic matter.
Contact Time
Higher concentrations require less contact time. For longer contact times like in RDWC, a lower concentration is required for optimal performance.
Addbacks refer to adding nutrients back into the system through the control bucket and are used to replenish the EC in the solution. In a DWC system, EC is constantly depleted by topping off the water and by plant consumption, so it is essential to replenish with nutrient addbacks.
This chart illustrates EC feathering up through addbacks over the course of a week, while RO maintains top-off.
This chart illustrates the relation between RO and EC through the life cycle of the plant. System water level stays consistent through automatic top-offs and changeouts when necessary.
WARNING: FAILING TO ACCOUNT FOR THE TOTAL VOLUME OF THE RDWC SYSTEM WHEN ADDING BACK NUTRIENTS CAN LEAD TO IMPROPER CONCENTRATIONS.
To increase the EC value of your RDWC system, follow this procedure.
The 2 Key Addback Variables:
• Target EC • Nutrient Recipe
ADDBACK EC CALCULATOR
Use this calculator to determine precise nutrient amounts. Input Stage, Week, System EC, Target EC and Operating Volume.
1 TARGET EC Determine what week you are in and your target EC.
2 SYSTEM EC Make sure system is at Operating Volume and check current EC.
3 ADDBACK EC Target EC - Actual EC = Addback EC
4 RECIPE Use the calculator to get the volume of each nutrient.
Do not start adding nutrients into your control bucket until you are at 75% of operating volume. If using an addback kit, the nutrients will not start flowing until the lower portion of the addback kit has been submerged.
NOTE: All nutrient parts are mixed into one 5 gallon addback tank. Do not dump into the control bucket, nutrients must be added through an addback kit.
WARNING: DO NOT ADD MORE THAN 500ML OF ANY ONE PART THROUGH A SINGLE ADDBACK TANK. IF YOUR ADDBACK REQUIRES ANY MORE THAN 500ML PER PART, USE MULTIPLE BUCKETS.
ADDBACK PROCEDURE
1 FILL Fill 5 gal bucket to 90% with RO water. (small addbacks, use 50%)
2 ADD Add required nutrients to the 5 gal bucket one at a time, maintaining the mixing order.
3 STIR Stir between adding each nutrient.
4 PUMP Slowly pump the mix into your system using an addback kit.
5 ADJUST Adjust the discharge valve to slowly dilute for 25 minutes.
6 WAIT Allow system to circulate for 30 minutes.
7 MONITOR Continuously monitor control bucket during discharge. If EC swings, slow down or dilute.
Verify system pH and EC with a second meter. Adjust pH if needed using the Addback Procedure.
Clean and calibrate your EC/pH probe.
RDWC CHANGEOUTS
Maintaining the right nutrient balance, pH, and EC levels is crucial for plant health in an RDWC system. Regular changeouts—either partial or full—are essential to address imbalances and prevent contamination. This guide will help you determine when to perform each type of changeout and provide step-by-step instructions to keep your system efficient and your plants thriving.
Draining down to the top of the bulkhead fitting and replacing the entire nutrient solution to address significant issues, such as major imbalances and reset the system. PARTIAL CHANGEOUT
CHANGEOUT TRIGGERS
3 week Veg time
pH fluctuating despite correction and full changeout this week.
Plants have drastically slowed eating despite stable parameters.
pH is rising/dropping more than allowable limits.
pH correction requires a steadily increased amount of buffer.
Plants slow nutrient uptake and needs more pH buffer.
Parameters fluctuated beyond limits due to operator error.
Post defoliation or between days 26-32.
10-14 days before harvest.
Flipping to Bloom after a 4 week or greater veg time.
Replacing 20-50% of the nutrient solution to correct minor imbalances and adjust water levels while keeping the system stable.
Changeout
Changeout
Changeout
RDWC CHANGEOUTS
Changeout procedures are vital for maintaining optimal RDWC system conditions. This section includes a tool for resetting your system and offers recommended timings and methods. However, the final decision on when and how to perform changeouts is up to the grower. Use these guidelines as a starting point and adjust based on your system’s needs.
Changeouts should be performed quickly and effectively.
WARNING: MINIMIZE THE TIME ROOTS ARE EXPOSED TO AIR TO PREVENT STRESS AND DAMAGE.
NOTE: Consistent monitoring and adjusting of pH and EC levels during these changeouts will ensure optimal nutrient availability and prevent buildup of harmful residues.
WARNING: DURING NUTRIENT SOLUTION CHANGEOUTS, ENSURE THAT THE SYSTEM IS POWERED OFF TO AVOID ELECTRICAL HAZARDS.
CHANGEOUT PROCEDURE
1 DETERMINE Determine what kind of changeout you need.
Determine volume of water.
RO Ensure there is enough RO water to fill the system to operating volume.
DRAIN Quickly drain your system.
Immediately refill with RO.
Add back nutrients using the Addback Procedure.
Check pH, EC, and water levels. Adjust as needed.
CHANGEOUT CALCULATION
This calculation shows how much nutrient solution to replace for optimal RDWC system conditions. Knowing the operating and left-over volumes ensures accurate changeouts.
Example Calculation for a 32-site system:
A. Operating volume: 33 modules × 10.6 gal = 350 gal
B. Left-over volume: 33 modules × 3 gal = 99 gal
C. Change-out volume: 350 gal - 99 gal = 250 gal
sure to include the control bucket in all volume calculations.
These icons are used in the top corner when on a page related to their stage.
Poke holes in the bottom of the expanded clay bag and rinse thoroughly with RO water.
PREPARE EXPANDED CLAY/MEDIA
Transfer the expanded clay into a clean 32-gallon bin.
Fill the bin to ¾ of its volume with RO water, then add 50 mL of pH down and 100 mL of Cleanse.
FILL THE SYSTEM
WARNING: DO NOT TRANSPLANT CLONES INTO A SYSTEM COLDER THAN 66 ° F. KEEP IN MIND THAT PH FLUCTUATES WITH TEMPERATURE.
Fill the system to the operating volume with RO water.
Start the circulation pump.
Stir the contents to ensure even distribution.
Transfer clay into another bin with holes and rinse again with RO water.
NOTE: Air manifold pressure is measured in Inches of Water Column. Be aware that system volume dictates the pressure.
Check all air stones to ensure they are bubbling uniformly and none are clogged.
Adjust the air manifold pressure to 26-28 inches of the water column gauge.
RDWC AIR STONES / AIR PUMPS
Air stones are essential because, without them, the plant would deplete the oxygen in the water, leading to poor water quality. The air pump ensures a constant flow of oxygen, maintaining a healthy environment for the plant. Only one standard 2” x 2” medium sized round air stone is needed per 8 gallon bucket. Larger than 13-gal buckets may require additional air stones, taking shape and volume into consideration.
Air stones should NEVER sit directly beneath the net pot. Too much turbidity can cause severe damage to new roots.
WARNING: ALITA BRAND AIR PUMPS OR SWEETWATER BLOWERS ARE RECOMMENDED TO PRESSURE YOUR AIR MANIFOLD. BLUE DIAMOND BRAND AIR PUMPS SHOULD BE STRICTLY AVOIDED.
Air pumps and blowers should be placed outside the flower room if the room is enriched with CO2.
Air stones should sit about 1” from the side of the bucket.
Air stones should be submerged at the bottom of the bucket.
Flower Room Wall Air Pump
13 Gal
8 Gal
NOTE: When viewed from the side, the water should just bubble over the structural ring directly beneath the planting deck.
Dunk net pots in a solution of RO water and 10 mL/gal of Cleanse to remove any factory dust and small plastic particles.
NOTE: Ensure the rockwool cube stays properly seated on the planting deck as the net pot is filled with media.
Place empty/clean net pots in multiple sites in the system.
Verify that the individual bucket volumes are relatively uniform and that the operating volume is correct.
WARNING: DO NOT PLACE FULL NET POTS ON FLAT SURFACES; EXPOSED ROOTS MAY BE CRUSHED OR DAMAGED.
Place the basal stem (or rockwool cube) on the planting deck, ensuring roots are positioned deeply.
Ensure the basal stem and any rockwool are above the water line to prevent stem rot.
Gently fill the net pot with expanded clay.
VEG CONSIDERATIONS
VEG – ROOM ENVIRONMENT
Fewer Addbacks
Plants may not eat immediately. It may take up to 5 days to see plants eating.
- 1.0 kPa
6 HRS: OFF 18 HRS: ON
VEG – SYSTEM PARAMETERS
Higher Nitrogen
Plants in the vegetative phase require higher nitrogen levels to support leaf and stem growth.
Long Light Periods
Provide 18 hours of light daily to encourage robust vegetative growth.
Training and Pruning
Apply low-stress training (LST) and topping techniques to control plant height and shape, promoting an even canopy.
VEG TIME: 2 WEEKS
Ideal for quick growth cycles, this option requires no nutrient solution change, saving time and resources.
Suitable for moderate growth periods, this option involves a partial nutrient solution change to maintain optimal plant health.
Best for extended growth cycles, this option requires a full nutrient solution change to ensure maximum nutrient availability and plant vitality.
Chart shows veg nutrients being used at changeout and bloom nutrients used for subsequent addbacks.
If flowering in a different room than the veg room, use this procedure.
WARNING: HANDLE ROOTS WITH EXTREME CARE TO AVOID DAMAGE. DAMAGED ROOTS CAN LEAD TO STRESS, SHOCK, OR EVEN PLANT DEATH.
Pull the lid off and pick up the plant
Walk over to the flower room.
Place into a clean 5-gallon bucket.
Place the plant into the 13-gallon flower bucket.
Repeat until all plants are transferred.
FLOWER – ROOM ENVIRONMENT
LIGHT SCHEDULE 12 HRS: OFF 12 HRS: ON
FLOWER – SYSTEM PARAMETERS
- 69° F
- 30”
FLOWER CONSIDERATIONS
More Addbacks
Nutrient uptake increases in this phase, requiring more frequent addbacks to maintain optimal EC levels.
Higher Phosphorus & Potassium
Shift to nutrients higher in phosphorus and potassium to support bud development.
Even Light Periods
Switch to a 12-hour light and 12-hour dark cycle to induce flowering.
Humidity Reduction
Lower humidity levels to prevent mold and mildew, keeping it around 40-50%.
FINISH – ROOM ENVIRONMENT
FINISH CONSIDERATIONS
Minimal Addbacks
During this phase, nutrient uptake is minimal, so addbacks are rarely needed.
Final Flush
Perform a flush with RO in the last 1-2 weeks to remove excess nutrients and improve the final product’s flavor and smoothness.
Trichome Monitoring
Check trichomes for maturity, looking for a mix of cloudy and amber trichomes to determine the ideal harvest time.
Temperature Drop
Slightly lower the temperature during the dark period to simulate fall conditions, which can enhance color and flavor.
RDWC LINE CLEANING
Renew Your Buckets
Irrigation buckets deliver critical nutrients to your crop. Biofilm and scale in your buckets can clog piping and airstones, giving inconsistent watering and nutrient delivery. Use Athena ® Renew between runs to clean your irrigation lines, remove inanimate scale, and prepare the surface for application of disinfectants. For older dirty lines that have been used with organic inputs, you may need to repeat cleaning several times in order to clear all the inanimate organic particulates out of the lines. Follow the step by step procedure to renew your irrigation system with Athena ® Renew and start clean every time.
Unplug Unplug the system’s circulation pump.
Drain Open the drain manifold and completely drain the system. (If not fitted, drain with the recirc pump and/or sump pump.)
Remove Remove net pots and lids, being careful not to get debris or grow media in the buckets.
Prep Leave air blower / air pumps running / air stones attached.
Vacuum Vacuum the buckets out.
Remove Remove the inline filters, close the return manifold valve, and suck out the recirc lines. Open Open the return manifold valve.
Dosing Compatibility
Athena ® Renew can be dosed into your control bucket with a Dosatron that is compatible with oxidizers. Other dosing systems require special seals such as Viton and Aflas that will allow them to dose acids or oxidizers.
Venturi based systems like Netaflex and Rhythm are not compatible with Athena ® Renew and should be hand mixed into your reservoir after the injection system. Dosing by hand into your reservoir is the safest way to avoid problems with injection systems.
Filters Take the inline filters to the sink and clean them with warm water and a toothbrush. Hold them up to the light for inspection.
Replace Replace the filter/filters.
Fill Fill the system up to operating volume with RO water. (11 gal per bucket for 13gal system, 6.5 gal per bucket in 8-gal system. Include the control bucket in the calculation for total system volume).
Reset Add 1 oz/gallon Reset in a few locations throughout the system.
Remove Remove the add-back-kit from the control bucket.
Vacuum Bring the vacuum to the control bucket and prepare to suck out any remaining old water/nutrient mix from the 1” corrugated recirc tubing when you start the circulation pump.
Pump Start the circulation pump and suck out 20 seconds of old water/nutrient mix. (Doing this will also help you prime the circulation pump.)
Circulate Allow the system to circulate overnight with the air stones bubbling.
CIRCULATION
Unplug
After sufficient circulation, unplug the system’s circulation pump.
Drain Open the drain manifold and completely drain the system. (If not fitted, drain with the recirc pump and/or sump pump.)
Scrub Scrub the inside of the buckets, focusing on the waterline, support ribs, control bucket, air lines, and DrainOut-Kit plug.
Inspect Use HID lighting or a strong LED flashlight to inspect buckets after walls have dried for residual scaling.
Vacuum
Vacuum the buckets out with the air stones still on and bubbling.
Remove Remove the In-Line-Filters, close the return manifold valve, and suck out the recirc lines.
Open Open the return manifold valve.
Filters Take the In-Line-Filters to the sink and clean them with warm water and a toothbrush. Hold them up to the light for inspection.
Replace Replace the filter/filters.
RO Fill the system with RO water to maximum operating volume.
WARNING: MAKE SURE TO
PROPER
WHEN HANDLING THESE PRODUCTS, INCLUDING
WITH RESPIRATOR, COVERALLS WORN OVER LONG-SLEEVED SHIRT AND LONG PANTS, SOCKS, CHEMICAL RESISTANT FOOTWEAR, AND WATERPROOF GLOVES.
CIRCULATION
Vacuum Vacuum the control bucket and prepare to suck out any remaining old water/nutrient mix from the 1” corrugated recirc tubing when you start the circulation pump.
Pump Start the circulation pump and suck out 20 seconds of old water/nutrient mix. (Doing this will also help you prime the circulation pump.)
Circulate Let the system circulate with the air stones bubbling for 20-30 minutes.
Unplug Unplug the system’s circulation pump.
Drain Open the drain manifold and completely drain the system. (If not fitted, drain with the recirc pump and/or sump pump.)
Fill Fill the system with RO water to approximately 1” above the bulkhead fittings
Pump Start the circulation pump and suck out 20 seconds of old water/nutrient mix. (Doing this will also help you prime the circulation pump.)
Circulate Let the system circulate with the air stones bubbling for 20-30 minutes.
Unplug Unplug the system’s circulation pump.
Drain Open the back drain out manifold ball valve to drain the system to just below the bulkhead fittings. (If not fitted, drain with the recirc pump or sump pump.
RO You are now ready to fill the system with RO water for the final time.
Pump Once the water reaches desired level, turn on the circulation pump and vacuum out old water for 20 seconds. Nutes Add nutrients and
RDWC PROGRAM
In RDWC every feeding uses the addback procedure, even for the initial system fill. Since addback EC varies every time, the actual recipe is always different. The most important thing is to maintain ratios of products to keep mineral levels optimal.
Use the Athena ® Addback Calculator to find the precise mL to hit your target EC for each week. Manual calculations use the below ratios and are discouraged due to potential errors.
DISCLAIMER - This is a baseline recommendation. Any adjustments made are at the growers discretion. Adjust the feed chart according to weeks needed to complete a run. Strain dependent.
NOTE: RDWC EC
System Volume
System Temperature
Circulation Pump
Air Pump
pH + PPM
Discharge Valve
System Smell
Meter Calibration
Leak Inspection
Date:
DAILY CHECKS (All Systems)
Check: Ensure water levels are consistent and at operating volume. Top off if necessary.
Check: Verify water temperature is within the optimal range for plant growth phase.
Check: Confirm the pump is operating correctly and there is good water flow.
Check: Ensure the air pump is running and providing adequate oxygenation.
Check: Measure and adjust pH and nutrient concentration levels as needed.
Check: Verify the valve is functioning properly and not clogged.
Check: Notice any unusual odors that might indicate problems like mold or algae.
Check: Ensure all measuring instruments are properly calibrated for accurate readings.
Check: Look for any leaks or drips in the system and fix them immediately.
pH is the most important parameter to adhere to. Note that pH may change rapidly after addback. Wait and then monitor because it will stabilize after inital push.
10 days before harvest, reduce the system temperature to 57°F to enhance plant colors. Note that temperatures below 62°F can reduce nutrient uptake.
Constantly top off systems with fresh RO water using a gravity feed or pressured manifold. Connect the float valve in the control bucket to the RO manifold to prevent fluctuations as plants drink.
Don’t use batch tanks for changeouts. Instead, we recommend mixing into an addback tank and feeding directly from the addback tank to the control bucket.
