RDWC Hydroponic Systems

Recirculating Deep Water Culture (RDWC) hydroponic systems create the ideal environment for explosive plant growth by combining three critical elements: continuous oxygenation, consistent nutrient delivery, and active water circulation. Unlike traditional Deep Water Culture (DWC) systems where each bucket operates independently, RDWC systems connect multiple grow sites to a central reservoir through large-diameter PVC piping. A submersible pump continuously circulates the nutrient solution from the reservoir through each grow site and back again, maintaining uniform water levels, pH, and nutrient concentrations across all plants.
The recirculating action serves multiple purposes. First, it prevents nutrient stratification—the tendency for heavier nutrient particles to settle at the bottom of standing water. Second, the constant movement helps maintain dissolved oxygen levels throughout the system. Third, it allows you to make adjustments in one central location that immediately affect all plants. This automation eliminates the tedious task of checking and topping off individual buckets, a major advantage over non-recirculating systems.
Each grow site features a large air stone connected to a high-capacity air pump, creating millions of tiny bubbles that maximize the dissolved oxygen content in the water. Plant roots absorb oxygen from the water, and this oxygenated environment allows them to uptake nutrients more efficiently than roots in soil. The combination of abundant oxygen and readily available nutrients enables plants to focus their energy on above-ground growth rather than developing extensive root systems to search for food and water.

Choosing the Right RDWC System Size for Your Space

2-Site RDWC Systems: Perfect for Beginners & Small Spaces

Our 2-site RDWC systems fit perfectly in 2x4 or 4x4 grow tents and are ideal for apartment dwellers, first-time hydroponic growers, or anyone wanting to test RDWC technology before committing to a larger setup. Despite their compact footprint, 2-site systems deliver all the benefits of larger configurations: automated circulation, consistent nutrient delivery, and superior oxygenation. These systems work exceptionally well for growing two large plants like cannabis, tomatoes or peppers. The smaller reservoir size (typically 5 gallons) means less nutrient solution to mix and lower initial costs, while still providing the expandability to add more sites later.

4-Site RDWC Systems: The Sweet Spot for Home Growers

The 4-site RDWC system represents the most popular configuration among home hydroponic gardeners, offering the perfect balance of productivity, manageability, and space efficiency. Designed to fit 4x4 or 5x5 grow tents—the most common tent sizes—a 4-site system provides enough growing capacity to supply a household with fresh produce year-round or accommodate a diverse garden with multiple plant varieties. The larger reservoir (5-8 gallons depending on model) provides more nutrient stability, requiring less frequent monitoring than smaller systems. Four plants also allow you to experiment with different varieties or stagger planting dates of some crops for continuous harvests.

6-Site & 8-Site RDWC Systems: Serious Growing Power

For dedicated hobbyists, small commercial operations, or growers with larger spaces, our 6-site and 8-site RDWC systems deliver serious production capacity. These larger configurations excel at feeding families, supplying local markets, or maintaining a year-round supply of fresh produce and herbs. The economies of scale become apparent at this size—you're managing the same single reservoir whether you have 4 plants or 8, but your harvest potential doubles. Larger systems also provide more thermal mass, meaning the nutrient solution temperature remains more stable throughout the day. Available in both 5-gallon and 8-gallon bucket configurations, these systems accommodate longer growing cycles and larger plants without the need for frequent reservoir changes.

RDWC vs DWC vs Other Hydroponic Systems: Which Is Right for You?

RDWC vs Standard DWC: Why Recirculation Matters

Standard Deep Water Culture systems feature individual buckets, each with its own air stone and nutrient solution. While DWC works effectively, it requires you to monitor and adjust each bucket separately—checking pH in four buckets, topping off four reservoirs, adjusting nutrients in four locations. This quickly becomes tedious and time-consuming. RDWC solves this problem by connecting all buckets to a central reservoir. Make one adjustment, and all plants benefit simultaneously. The active circulation also prevents the nutrient imbalances that can occur in stagnant DWC buckets, where plants may deplete specific nutrients faster than others, creating deficiencies.
Beyond convenience, recirculation improves plant health. The flowing water helps maintain more consistent dissolved oxygen levels throughout the system, whereas static DWC buckets may develop oxygen-depleted zones. RDWC systems also maintain more stable pH levels because the large volume of circulating water resists rapid pH swings that can stress plants. For growers managing 4 or more plants, RDWC's automation and consistency make it the clear winner over standard DWC.

RDWC vs Dutch Bucket Systems: Different Tools for Different Jobs

Dutch bucket (Bato bucket) systems use drip irrigation to periodically water plants growing in media like coco coir, perlite or clay pebbles. The siphon elbows in each bucket maintain a small reservoir at the bottom while excess solution drains back to the main reservoir. Dutch buckets excel at growing large, vining plants like tomatoes, cucumbers, and peppers, particularly in greenhouse settings or outdoor applications. They're more forgiving of power outages (plants can survive longer without irrigation than without aeration) and work well with natural sunlight.
RDWC systems, conversely, keep roots continuously submerged in water, requiring reliable power for both circulation and aeration pumps. This makes them ideal for indoor growing with artificial lighting, where environmental control is already a priority. RDWC typically delivers faster growth rates than Dutch buckets because roots have 24/7 access to nutrients and oxygen, whereas Dutch bucket plants must wait for the next irrigation cycle. However, RDWC requires more attention to water temperature and dissolved oxygen levels. Choose Dutch buckets for greenhouse growing and large vining plants; choose RDWC for faster-growing crops, indoor setups, and maximum yield in controlled environments.

RDWC vs NFT (Nutrient Film Technique): Flow Rate & Root Mass

NFT systems flow a thin film of nutrient solution through channels or tubes where plant roots dangle. NFT works beautifully for lightweight, fast-growing crops like lettuce, herbs, and strawberries but struggles with larger plants that develop extensive root masses. As roots grow, they can block the channel, creating uneven flow and dead zones. NFT also requires careful slope calibration and is vulnerable to pump failures—if flow stops, roots dry out quickly.
RDWC systems handle both small and large plants equally well. The substantial volume of water in each bucket provides a buffer against pump failures, and the large-diameter PVC piping resists clogging even with mature root systems. RDWC's deep water reservoir in each bucket supports heavier plants better than NFT channels. For growers wanting versatility—the ability to grow everything from lettuce to tomatoes in the same system—RDWC offers more flexibility than NFT's specialized design.

Essential Components of a Quality RDWC System

Grow Buckets: Why Size and Material Matter

The foundation of any RDWC system is the grow buckets themselves. Our systems use thick-walled, food-grade square buckets in either 5-gallon or 8-gallon capacities. Square buckets offer significant advantages over round buckets: they maximize space efficiency in rectangular grow tents, their flat sides create better seals with bulkhead fittings (reducing leak potential), and they provide more usable volume for the same footprint. The opaque black material prevents light penetration, which is critical for preventing algae growth in your nutrient solution.
Size selection depends on your growing cycle and plant type. Five-gallon buckets work perfectly for most vegetables, herbs, and shorter growing cycles (8-12 weeks). The smaller water volume makes nutrient changes easier and less expensive. Eight-gallon buckets suit longer growing cycles, larger plants, or situations where you want maximum buffer against water level fluctuations. Tomatoes, peppers, cannabis and other crops staying in the system for 10+ weeks benefit from the additional root space and water volume of 8-gallon buckets.

Pumps: Circulation and Aeration Requirements

Every RDWC system requires two types of pumps: a water circulation pump and an air pump. The circulation pump, typically rated between 250-400 GPH (gallons per hour), sits in the reservoir and pushes nutrient solution through the system. Proper flow rate is crucial—too slow and you risk nutrient stratification and inadequate oxygen distribution; too fast and you may create excessive turbulence that stresses roots. Our systems include appropriately sized pumps that circulate the entire system volume every 15-20 minutes, the ideal rate for most crops.
The air pump supplies oxygen via air stones in each grow site. Dissolved oxygen is arguably the most critical factor in hydroponic success—roots need oxygen to function, and oxygen-deprived roots quickly develop root rot (pythium). We include high-capacity air pumps (typically 35+ liters per minute for 4-site systems) with multiple outlets, ensuring each bucket receives strong, consistent aeration. The large air stones create fine bubbles with maximum surface area for oxygen transfer. Never skimp on aeration—it's the difference between thriving plants and disappointing results.

PVC Piping and Connections: The Circulation Highway

Our RDWC systems use 50mm (approximately 2-inch) PVC piping to connect grow sites. This large diameter is intentional—it minimizes flow restriction and allows roots that may grow into the pipes to pass through without causing blockages. Smaller diameter tubing (3/4-inch or 1-inch) common in economy systems creates bottlenecks that reduce circulation effectiveness and are more prone to clogging.
The connection system features rubber-sealed elbows and straight bulkhead fittings that simply screw together—no gluing, no special tools, no mess. This makes assembly and disassembly straightforward for cleaning and maintenance. The tight rubber seals prevent leaks while remaining easy to disconnect when you need to modify your system or add expansion kits. Quality of connections directly impacts system reliability, and our commercial-grade fittings ensure leak-free operation throughout your growing season.

Setting Up Your RDWC System: Step-by-Step Guide

Location and Space Requirements

Before assembling your RDWC system, select an appropriate location that meets several key requirements. First, ensure the floor is level—uneven surfaces cause unequal water distribution between buckets and can stress PVC connections. A concrete basement floor, level wooden platform, or properly adjusted grow tent is ideal. The location should support the system's weight when full: a 4-site RDWC system with 5-gallon buckets holds approximately 25 gallons of water, weighing over 200 pounds plus equipment and plants.
Consider proximity to water sources for reservoir filling and changing, access to power outlets for pumps and lighting, and adequate drainage in case of leaks. Indoor systems benefit from grow tents that contain humidity and simplify environmental control, but ensure your tent provides enough height clearance—you need space above the buckets for plant growth plus lighting distance. A 4x4 tent with 6-7 feet of height accommodates most 4-site systems comfortably. Finally, consider ventilation—healthy plants transpire significant water, and proper air exchange prevents humidity problems and strengthens stems.

Assembly and Initial Setup

Start by laying out all components according to the instruction manual. Connect the grow buckets to the central reservoir using the PVC piping system—straight connectors link buckets in a row, while elbows connect to the reservoir. Most 4-site systems arrange in a rectangular pattern with the reservoir at one end, but configurations vary. Ensure the rubber-seals are on both sides of the grow buckets when tightening the fittings. Fill the reservoir with water (without nutrients initially) and run the circulation pump to check for leaks before adding plants or expensive nutrients.
Install the air pump in a cool location above the water level to prevent water from siphoning back into the pump during power outages. Connect air line tubing from each pump outlet to an air stone, placing one stone in each grow bucket. Ensure air stones rest on the bucket bottom and are positioned away from the water inlet to promote circulation. Attach net pots to the bucket lids, filling them with your chosen growing media—clay pebbles (hydroton) are most popular due to excellent drainage and reusability.

Water Quality and Initial Nutrient Mixing

Water quality significantly impacts hydroponic success. Most municipal tap water works fine, but let it sit for 24 hours to allow chlorine to evaporate, or use a carbon filter, dechlorinated water may also be used. Test your water's starting pH and EC/PPM (electrical conductivity or parts per million). Most tap water ranges from pH 7-8 and contains 150-300 PPM of dissolved minerals. Hard water (high calcium/magnesium) may require more pH down adjustments and affects nutrient calculations.
For initial setup with seedlings or young plants, mix nutrients to 400-600 PPM (EC 0.8-1.2) and adjust pH to 5.8-6.2. The mild solution prevents shock to young roots. As plants mature, gradually increase nutrient strength to 800-1200 PPM (EC 1.6-2.4) depending on crop type and growth stage. Use a quality hydroponic nutrient designed for recirculating systems—these include micronutrients and maintain stability in solution. Follow the manufacturer's feeding schedule as a starting point, adjusting based on your plants' response. Always adjust pH AFTER adding nutrients, as nutrients affect pH.

Maintaining Your RDWC System for Optimal Results

Daily Monitoring: The 5-Minute Check

Successful RDWC growing requires brief daily monitoring—typically 5 minutes once you establish a routine. Check water level in the reservoir (roots should remain submerged in buckets with water level 1-2 inches below the net pot). Top off with pH-adjusted water as needed, adding back a diluted nutrient solution (half-strength) if PPM has dropped significantly. This practice, called "top-off solution," helps maintain stable nutrient concentrations as plants consume water faster than nutrients.
Observe plant health from across the room—dark green leaves growing at expected rates indicate proper nutrition. Yellowing, tip burn, stunted growth, or wilting signals problems requiring investigation. Check that both pumps operate correctly: listen for the air pump's hum and see bubbles in each bucket; observe water flowing from the circulation pump in the reservoir. Verify water temperature stays between 65-72°F—higher temperatures reduce dissolved oxygen and encourage root pathogens. A simple aquarium thermometer provides continuous monitoring.

Weekly Tasks: Maintaining System Health

Once weekly, test pH and PPM/EC levels with meters rather than relying on estimation. pH tends to drift upward as plants consume nutrients, requiring periodic adjustment with pH down solution. PPM gradually decreases as plants uptake nutrients—if PPM drops below your target range, add additional nutrients. Conversely, if PPM remains stable or rises while water level drops, plants are consuming water faster than nutrients, suggesting you should lower nutrient concentration.
Inspect roots by lifting a net pot—healthy roots appear white or light tan with tiny fuzzy root hairs. Brown, slimy, or foul-smelling roots indicate root rot (pythium) requiring immediate treatment. Check all connection points for moisture that might signal slow leaks. Wipe down bucket exteriors and remove any algae from lids or exposed surfaces. Clean the reservoir area and ensure no standing water exists outside the system. These quick inspections prevent small issues from becoming major problems.

Biweekly Reservoir Changes: Fresh Start

Every 1-2 weeks (weekly for fast-growing crops, biweekly for slower growers), completely drain and replace the nutrient solution. Over time, plants deplete certain nutrients faster than others, creating imbalances that can't be corrected by simply adding more nutrients. pH buffering capacity decreases, making pH harder to control. Salts accumulate, and organic matter from root cells builds up. A complete reservoir change resets the system to known conditions.
Operate drain valves or use a submersible pump to drain the reservoir into a waste container or down a drain. Wipe out the reservoir interior with a clean cloth. Rinse buckets and reservoir with fresh water to remove accumulated salts. Some growers include a mild hydrogen peroxide solution (1ml per gallon) during rinse to sanitize the system. After rinsing, fill with fresh water and mix a new batch of nutrients according to your feeding schedule. This is an excellent time to inspect roots and prune any brown or dead material.

Troubleshooting Common RDWC Issues

Root Rot (Pythium): Prevention and Treatment

Root rot, caused by pythium and other water molds, is the most serious threat to hydroponic systems. Symptoms include brown, slimy roots with a distinctive musty or rotten smell, along with wilting plants despite adequate water. Pythium thrives in warm, oxygen-poor conditions, so prevention focuses on maintaining water temperature below 72°F and ensuring strong aeration. Beneficial bacteria products (like Hydroguard or Southern Ag Garden Friendly Fungicide) colonize roots and outcompete pathogens, providing excellent prevention.
If root rot appears, act immediately. Remove affected plants and trim away all brown, dead root material using sterilized scissors. Drain and thoroughly clean the entire system, including a sanitizing rinse with diluted hydrogen peroxide or commercial sanitizer. Replace nutrients and add beneficial bacteria or hydroponic-safe fungicide. Increase aeration if possible and verify water temperature stays cool. Consider adding a water chiller if warm ambient temperatures make cooling difficult. Caught early, plants often recover; severe cases may require starting over.

pH Fluctuations: Keeping Things Stable

pH instability frustrates new growers, but understanding the causes helps. Young plants typically cause pH to rise as they consume nitrate nutrients, which increases alkalinity. Adjust downward using pH down solution (typically phosphoric acid) in small increments—0.5 pH points per adjustment maximum, allowing 15 minutes between tests for equilibrium. Large pH swings stress plants and can cause nutrient lockout where roots can't absorb available nutrients despite adequate PPM.
Persistent pH instability often indicates issues beyond normal drift. Very hard water with high mineral content resists pH adjustment and may require an RO (reverse osmosis) water filter. Algae growth produces oxygen during daylight and consumes it at night, causing pH swings—prevent by ensuring no light enters the reservoir or buckets. Root problems release organic acids that drop pH. An insufficient reservoir volume relative to plant size provides too little buffer, causing rapid changes. Upgrading to larger buckets or adding reservoir capacity improves stability in such cases.

Nutrient Deficiencies and Toxicities: Reading Your Plants

Plants communicate nutrient issues through leaf symptoms. Nitrogen deficiency shows as yellowing of older, lower leaves as the plant relocates mobile nutrients to new growth. Excess nitrogen causes dark green leaves and weak, stretchy stems. Phosphorus deficiency produces purple or red leaf undersides and slow growth. Potassium deficiency appears as brown, crispy leaf edges (tip burn). Calcium deficiency affects new growth with deformed leaves and is common in RO water systems lacking adequate cal-mag supplementation.
Iron, manganese, and other micronutrient deficiencies typically indicate pH problems rather than actual nutrient absence—these elements become unavailable outside the 5.5-6.5 pH range. Before adding more nutrients, verify pH falls within acceptable range. Take photos of symptoms and compare to nutrient deficiency charts widely available online. Make one adjustment at a time and observe results over 3-5 days before making additional changes. Overreacting with multiple corrections simultaneously makes diagnosis impossible and can create cascading problems.

Advanced RDWC Techniques for Maximum Yields

Plant Training and Support in RDWC Systems

RDWC systems support various plant training techniques to maximize yields within limited spaces. Low-stress training (LST) involves gently bending and securing stems to create a level canopy where all growth tips receive equal light exposure. Use soft ties or flexible wire to anchor stems to the bucket lids or a support structure. Screen of Green (SCROG) places a horizontal net 12-18 inches above buckets, weaving plant stems through the mesh as they grow. This creates an even canopy while supporting heavy fruit loads.
Topping—removing the main stem's growing tip—causes plants to develop multiple main colas rather than a single central stem. Combined with LST or SCROG, topping produces bushier plants with more flowering sites. For tomatoes and peppers, single-stem training with vertical support maximizes vertical space. Use tomato cages or string trellises attached to overhead support. Prune lower leaves to improve air circulation and direct energy to fruit production. RDWC's rapid growth allows plants to recover quickly from training stress, unlike slower soil-grown plants.

Environmental Control: Dialing In Your Grow Room

While RDWC automates nutrient delivery, environmental conditions remain your responsibility. Temperature affects everything—aim for 70-78°F during lights-on periods, dropping 10-15°F during lights-off to simulate natural day/night cycles. Humidity should match plant growth stage: 65-70% for seedlings, 55-60% during vegetative growth, and 45-50% during flowering to prevent mold on dense flower clusters. Use humidifiers, dehumidifiers, and exhaust fans to maintain targets.
Lighting intensity and duration dramatically impact growth rates and yields. LED grow lights offer the best efficiency, but ensure adequate wattage for your space (30-40 watts per square foot minimum for flowering). Maintain appropriate distances between lights and canopy—too close causes heat stress and bleaching; too far reduces intensity and stretches plants. Use a timer for consistent photoperiods: 18 hours on/6 hours off for vegetative growth, 12/12 for flowering in photoperiod plants. CO2 supplementation (1200-1500 PPM) can increase growth rates 20-30% when all other factors are optimized.

Crop Steering: Manipulating Water Availability

Advanced growers use crop steering techniques to influence plant behavior by adjusting irrigation frequency, EC levels, and water content in growing media. While traditional RDWC keeps roots constantly submerged, some growers modify their systems with ball valves to create temporary low-water periods that stress plants slightly, triggering defensive responses like increased essential oil production or accelerated flowering. This mimics natural cycles where plants prepare for dry periods.
In standard RDWC operation, steering focuses on EC manipulation. Higher EC (1400-1800 PPM) during early flowering promotes denser, more compact growth. Lower EC (1000-1200 PPM) during late flowering with increased potassium ratios encourages swelling and ripening. Combined with controlled day/night temperature differentials, these techniques let skilled growers fine-tune plant morphology and chemical composition. Experimentation is key—document your techniques and results to develop custom protocols for your specific varieties and goals.

Getting Started: Your Next Steps

Starting with RDWC hydroponics opens the door to faster growth, higher yields, and year-round gardening independence. Whether you're growing fresh salads in a spare bedroom, cultivating gourmet herbs for your kitchen, growing craft cannabis or producing tomatoes and peppers that outperform anything from the grocery store, RDWC systems provide the automated convenience and performance results that make hydroponic growing rewarding rather than burdensome.
Begin by selecting a system size that matches your available space and growing ambitions. Two-site systems let you dip your toes in with minimal investment. Four-site systems offer the sweet spot for most home growers. Larger systems suit dedicated hobbyists ready to maximize production. All our systems ship with complete components, detailed instructions, and access to our growing support community. Within hours of delivery, you'll have plants growing in your new RDWC system.
Success comes from consistency rather than perfection. Maintain your daily 5-minute monitoring routine, change reservoirs every 1-2 weeks, and keep notes on what works for your specific setup and varieties. Join online hydroponic communities to learn from experienced growers and share your own successes. With each growing cycle, your skills and confidence will increase. Before long, you'll be the one answering questions and sharing advice with new growers. Welcome to the RDWC growing community—your journey to hydroponic mastery begins today.