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Professional Recirculating Deep Water Culture for Large-Plant Spacing and Maximum Yields
The Current Culture H2O UCXXL13 is a 13-gallon Recirculating Deep Water Culture (RDWC) system engineered for growers who want bigger plants, more canopy space, and higher yields. With 40″ plant spacing, it’s perfect for large-format crops, providing unrestricted room for growth while delivering aerated nutrient solution 24/7 for optimal root health.
For over two decades, Under Current® systems have set the standard for professional hydroponics, offering simple, reliable, and repeatable results in both commercial and personal grows.

✅ Quick-Glance Benefits
| 💧 Medium-Less Growing No rockwool, coir, soil, peat, or grow rocks required |
| ⚙️ Semi-Automated Operation No timers or complex schedules — just maintain nutrient balance |
| 🛡️ Built-In Redundancy Water and air pumps ensure optimal plant conditions 24/7 |
| 🌱 Large-Plant Spacing 40″ centers allow maximum canopy development |
| 📈 Consistent Yields Delivers premium-quality harvests cycle after cycle |
What’s Included
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UCXXL13 RDWC Modules – 13-gallon capacity, 40″ plant spacing
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High-Flow Manifold & Plumbing Kit
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Water Pump & Air Pump
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Aeration Components
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Installation & Operation Guide
Use It For
✔️ Commercial cannabis production
✔️ Hydroponic vegetable growing
✔️ Greenhouse or indoor facilities with large plants
✔️ Consistent, large-scale harvests
🔍 Standout Features
| 🌀 Continuous Aeration Aerated nutrient solution circulates 24/7 to all sites |
| 🛠️ Easy to Use No crop steering or guesswork required to get results |
| 🏆 Industry Standard Trusted by professionals for over two decades |
Ready to grow bigger and better?
Order the Current Culture H2O UCXXL13 RDWC System today and take advantage of large-plant spacing for exceptional yields and plant health — all with the simplicity of RDWC.
Specifications – Current Culture H2O UCXXL13 RDWC System
System Type: Recirculating Deep Water Culture (RDWC)
Module Capacity: 13 Gallons Each
Plant Spacing: 40″ Centers
Number of Sites & Rows
4-SITE, 2-ROW, 6-SITE, 2-ROW, 8-SITE, 2-ROW, 12-SITE, 2-ROW, 16-SITE, 2-ROW, 9-SITE, 3-ROW, 12-SITE, 3-ROW, 18-SITE, 3-ROW, 24-SITE, 3-ROW, 16-SITE, 4-ROW, 24-SITE, 4-ROW, 32-SITE, 4-ROW
User Manual – Current Culture H2O UCXXL13 RDWC System
Warranty – Current Culture H2O UCXXL13 RDWC System
Manufacturer Warranty: Varies by component
Covers defects in materials and workmanship
Support handled directly through manufacturer or via our team
FAQ
What are the most common mistakes made in water culture?
a. Running nutrient strength too high. This can inhibit water uptake and contribute to metabolic stagnation and subsequent plant stress.
b. Using incompatible inputs in solution causing convolution of the water chemistry. Avoiding organic, low solubility inputs is strongly recommended.
c. Micromanaging pH. Adjusting pH too frequently can lead to nutrient solution instability and issues.
What makes the Under Current a more efficient hydroponic method?
Less frequent nutrient change outs, lower nutrient usage rates, less pH fluctuations (less pH adjusters needed) and the conservation of precious H2O.
What makes the Under Current more productive compared to other hydroponic systems?
When a water culture system is operated properly, plants benefit from an increased uptake of water and minerals in solution as well as sustained cell turgidity. Given the favorable CEC of water, a plants nutrient uptake efficiency in water culture is very high, resulting in superior results.
Planning And Sizing
What is the approximate volume of solution in each module during standard operation?
a. 8 gallon – approx. 6 gallons
b. 13 gallon – approx. 10 gallons
c. 35 gallon – approx. 30 gallons
How do I calculate my total system volume?
a. Multiple total number of modules plus 1 (for Epicenter) multiplied by the approximate volume per module. Take this volume and add 10% to account for solution in joints and manifolds.
b. Example: UCDB16XL –
i. 17 x 6 gallons per module = 102 gallons
ii. 102 + 10% = 112 gallons
Can I integrate a nutrient auto dosing system?
Yes.
What is a top-off reservoir and why do I need one?
A top-off reservoir is used to maintain consistent system volume and water chemistry. The top-off reservoir will supply solution via gravity to the float valve in Epicenter (control module).
Do I need a water chiller?
Yes.
Do I need a Bulkhead Filter for each growth module?
No.
Is there an option for custom system spacing?
Yes, all systems are available in a “Boneless” configuration without straight sections of pipe, allowing you to customize your plant centers.
Does a "Boneless" system include instructions on how to cut/couple pipe?
Yes, each “Boneless” kit includes a Boneless cut chart and recommendations for gluing and assembly.
Operating the Under Current
Should the Air Pump and Water Pump run 24/7?
Yes.
Where should I set my solution level?
a. Initial Transplant: See diagram.
b. Veg: 2” above base of net pot.
c. Bloom: 1” below base of net pot
What should be in my top-off reservoir?
When operated properly, top off should be balanced the same or slightly higher as the solution in the system.
Does a top-off reservoir help maintain water chemistry (pH/EC) stability?
Yes. Any fluctuations in pH/EC can have a negative effect on plant health.
How do I adjust pH?
a. CAUTION: Do NOT add pH concentrate directly to Epicenter (control module).
b. If the pH is between 5.5-6.5 no adjustment is necessary.
c. Dilute pH adjuster 1:128 (about 1 oz. adjuster per gallon of fresh water). Once diluted slowly add to the system, allow 20-30 minutes for mixing. Re-test once pH has stabilized, add more diluted adjuster as necessary.
What solution temperatures are optimal?
We recommend maintaining a water temperature between 65-68 degrees F.
What solution temperatures are optimal?
We recommend maintaining a water temperature between 65-68 degrees F.
Do I need to include the initial PPM of my source-water when calculating nutrient levels?
Yes. Adjust accordingly.
Do I need to include the initial PPM of my source-water when calculating nutrient levels?
Yes. Adjust accordingly.
Do I have to empty out the entire system to do a nutrient change-out?
No.
What do I use to clean the system? Mix Ratio of Cleaning Agent?
Physan 20, follow manufacturer’s directions.
Growing in the Under Current
How do you veg for the system?
a. Under Current system (8 gallons): Bare root or cube (rock wool, oasis, etc) propagated plants can be placed directly into our CCH2O Net Pot and placed directly into a Under Current system for optimum growth. This technique is perfect if subsequently transplanting into a larger Under Current system (13 gallon or 35 gallon PRO) at a wider plant spacing.
i. In this case, the entire CCH2O Lid (with Net Pot) can be picked up and moved directly to another Under Current growth module for flowering. This method is ideal for avoiding unnecessary root damage during transplant into bloom.
b. Ebb and Flow table (Periodic Flood): Bare root or cube (rock wool, oasis, etc) propagated plants can be placed directly into our CCH2O Net Pot or 4″/6″ rock wool cubes and placed in a typical tray. Some natural root pruning may occur as the roots grow through the net pot due to the intermittent watering cycle.
c. Ebb and Flow Table (Continuous Flood): Bare root or cube (rock wool, oasis, etc) propagated plants can be placed directly into our CCH2O Net Pot or 4″/6″ rock wool cubes and placed in a typical tray. Adding air diffuser to the tray will create a water culture environment. This will stimulate root growth similar to the Under Current system and prepare the plants for a fairly seamless transition.
d. Drip: Bare root or cube (rock wool, oasis, etc) propagated plants can be placed directly into our CCH2O Net Pot or 4″/6″ rock wool cubes. A drip system with emitters in each net pot/cube can be placed on a bench or in a flood tray. Some natural root pruning may occur as the roots grow through the RW cube.
What grow mediums are recommended for use in the Under Current?
a. Any non-wicking inert grow media tends to work best. Expanded clay pellets and growstones are some of the most popular.
b. When using a wicking media like rockwool be sure to adjust solution level to ¼” below contact with the R.W.
Nutrient Considerations
What is the best nutrient for the Under Current?
Pure mineral-salt based nutrients like Current Culture’s Cultured Solutions are the most compatible with actively aerated water culture.
What is the recommended nutrient strength for the Under Current?
a. Veg: 100-400 ppm / 0.2-0.8 EC
b. Bloom: 450-900 ppm / 0.9-1.3 EC
c. **Based on ppm 500 scale
Are carbohydrates/sweeteners, enzymes and beneficial bacteria recommended in the Under Current?
No. These tend to create bio-films and de-stabilize water chemistry.
Should I use Ca/Mg in the Under Current?
When using Reverse Osmosis (RO) or De-Ionized (DI) water Calcium Magnesium is recommended at 0.25-1mL per gallon. The Cultured Solution’s Coco Cal Supplement is your best choice.
Should I change my nutrient strength each week?
Follow manufacture’s nutrient schedule as recommended.
How frequently should I change my nutrients?
Change outs are recommended every 7 to 14 days, or if pH becomes de-stabilized (drifts more than 0.3 per day).
Do I need to flush my system between change-outs?
No, assuming only compatible inputs are being used a simple drain and refill is sufficient.
Is it possible to over-aerate my Under Current?
Yes, we recommend aeration levels stay between 0.75-1.5 liters per minute/per gallon. Exceeding these levels may cause mineral precipitation and nutrient de-stabilization.
Shipping Policy
Free Shipping Within the Continental U.S.
We offer free shipping on all orders over $200 shipped to addresses within the continental United States. Orders under $200 will have shipping calculated at checkout. There are no hidden fees or handling charges. The price you see at checkout is the final price you pay.
Order Processing
Orders are typically processed within 1–2 business days (Monday–Friday). If an item is temporarily backordered or delayed, we’ll notify you by email with an updated shipping estimate.
Shipping Confirmation & Tracking
Once your order has shipped, we’ll email you a shipping confirmation that includes tracking information. You can use this to monitor the delivery status of your package in real time.
Where Orders Ship From
We partner with trusted suppliers and manufacturers who maintain warehouse locations throughout the United States. Orders are typically shipped from the facility closest to your delivery address to ensure faster transit times and greater efficiency. Some orders may ship in multiple packages depending on item availability and warehouse location.
Estimated Delivery Time
Most orders arrive within 3–7 business days of shipping, depending on your location and the item’s warehouse origin. Freight items and oversized packages may take additional time.
Shipping Carriers
We use trusted carriers such as FedEx, UPS, USPS, and professional freight delivery services for large or heavy items. Depending on the size of your order, it may arrive in multiple packages or from multiple warehouses.
Delivery and Moving Disclaimer
Please note: We do not offer moving or installation services. For freight shipments or large items, carriers are only responsible for curbside delivery. Drivers are not required to move items inside your home, up stairs, or to specific locations. We strongly recommend having assistance available at the time of delivery for heavy or bulky shipments.
Address Accuracy & Order Changes
Please ensure your shipping address is correct at the time of checkout. Once an order has shipped, we are unable to change the delivery address or reroute the shipment. If you need to make changes to your order, contact us immediately after placing it.
Damaged or Lost Shipments
If your order arrives damaged or appears to be lost in transit, contact us within 48 hours of delivery (or expected delivery). We will work with the carrier to resolve the issue as quickly as possible.
Shipping Restrictions
We currently ship only to addresses within the continental United States. We do not ship to Alaska, Hawaii, U.S. territories, or international destinations.
Questions?
If you have questions about your order, delivery, or shipping process, feel free to reach out to us through our Contact Us page or via email (sales@gardengrowshop.com ). We’re here to help.
Start of Returns section
Easy Returns, No Surprises
At Garden GrowShop, we stand behind the quality of every product we carry. But we also understand that sometimes things just don’t work out — and that’s okay. If you change your mind or the item isn’t quite what you expected, we’ve got you covered.
30-Day Return Guarantee
You have 30 days from the date of delivery to request a return for any reason. To start a return, simply email us at sales@gardengrowshop.com with your order number and we’ll walk you through the process.
Here’s what to expect:
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You’ll receive clear return instructions from our team.
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Once your item is received and inspected, we’ll issue a refund to your original payment method.
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Items must be returned in “like new” condition, with all original packaging and accessories.
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Return shipping costs are the responsibility of the customer.
“Like new” means no visible wear, damage, or missing parts. Items showing signs of use or misuse may not qualify for a refund.
Damaged or Defective Orders
If your order arrives damaged or defective, don’t worry — we’ll take care of it.
Here’s what to do:
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Note any damage with the delivery driver when signing for the package.
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Email photos and a description of the issue to sales@gardengrowshop.com on the same day you receive it.
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We’ll cover the cost of return shipping and make sure a replacement is sent out quickly.
Please keep all original packaging in case a return is needed. This helps speed up the process and ensures a smooth resolution.
Order Cancellations
If you need to cancel your order, please contact us as soon as possible at sales@gardengrowshop.com or by phone.
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Cancellations before shipment receive a full refund.
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Cancellations after shipment will follow our standard return policy and may be subject to return shipping costs.
Important Return Notes:
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Certain products may have brand-specific return restrictions, which will be noted on the product page.
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Products purchased for temporary or single-use purposes (e.g. trade shows, promotional events) are not eligible for return.
We’re Here to Help
Our goal is to make returns and exchanges as easy as possible — with no stress and no surprises. If you’re unsure whether your order qualifies or just want to ask a question, don’t hesitate to reach out. We’re here to make sure you feel confident before and after your purchase.
Why Garden GrowShop?
We’re an authorized dealer for every brand we sell—so you’ll always get full manufacturer warranties, premium support, and authentic gear direct from the source.
✅ Fast, tracked shipping on all orders
✅ 100% safe and secure checkout
✅ No restocking fees on returns
✅ Friendly U.S.-based support when you need it
Have questions? We're here to help. Whether you're just getting started or scaling up a full grow, our experts can guide you to the right gear.
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