Under Current Hydroponic System FAQ

Under Current FAQ’s


Simplify your grow and you may find yourself with more time. When used properly the UC will give you lots of extra time. You can’t buy that in a bottle.


1. 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. Micro managing pH. Adjusting pH too frequently can lead to nutrient solution instability and issues.

2. 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.

3. 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.


4. 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

5. 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

6. Can I integrate a nutrient auto dosing system?

Yes. Visit the Automation section on www.cch2o.com for more information.

7. 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. Top-off reservoir will supply solution via gravity to the float valve in Epicenter (control module).

10. 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.

11. 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.


13. 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

14. 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.

15. Does a top-off reservoir help maintain water chemistry (pH/EC) stability?

a. Yes. Any fluctuations in pH/EC can have a negative effect on plant health.

16. 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 system, allow 20-30 minutes for mixing. Re-test once pH has stabilized, add more diluted adjuster as necessary.

17. What solution temperatures are optimal?

We recommend maintaining a water temperature between 65-68 degrees F.

20. What do I use to clean the system? Mix Ratio of Cleaning Agent?

Physan 20, follow manufacturer’s directions.


21. How Do You Veg For the System?

a. Under Current system (8 gallon): 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 simulate 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.

22. 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.


23. What is the best nutrient for the Under Current?

Pure mineral-salt based nutrients are the most compatible with actively aerated water culture.

24. 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

25. Are Carbohydrates/Sweeteners, Enzymes and Beneficial Bacteria recommended in the Under Current?

No. These tend to create bio-films and de-stabilize water chemistry.

26. 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.

27. Should I change my nutrient strength each week?

Follow manufacture’s nutrient schedule as recommended.

28. How frequently should I change my nutrients?

Change outs are recommended every 14-21 days, or if pH becomes de-stabilized (drifts more than 0.3 per day).

29. Do I need to flush my system between change-outs?

a. No, assuming only compatible inputs are being used a simple drain and refill is sufficient.

30. 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.


31. What should I do if I make a mistake?

Observations and slight adjustments are the best way to dial your system in, when in doubt give CCH2O a call.