Why Closed-Loop Irrigation Is the Smart Choice for Coco and Perlite Grows
If you’re growing in coco/perlite—or perlite-only medium—you already know how fast these mediums drain. That’s a blessing and a curse: while you avoid waterlogging and get great airflow, it also means you’re flushing out nutrients with every feed. Unlike soil, where excess water is slowly absorbed, these mediums require a minimum of 10–20% runoff per feed to prevent salt buildup and nutrient toxicity. And if you’re still using an open irrigation system, you’re literally watching your nutrients (and money) go down the drain.
That’s where closed-loop irrigation comes in.
It’s a smarter, cleaner, and more efficient way to water your grow. Whether you’re running a single tent or managing a multi-room hydro setup, closed-loop irrigation gives you control, consistency, and reuse with minimal risk. It significantly reduces the chance of flooding by managing runoff and also makes nutrient dosing stations or injectors easier to integrate.
Note: Closed-loop systems are only suitable for inert media like coco and perlite—not soil—due to the risk of clogging, decomposition, and microbial instability.
What Is a Closed-Loop Irrigation System?
A closed-loop system captures the runoff, filters it, and reuses it. Instead of feeding your plants and letting the excess run into waste buckets or drains, the system collects runoff in a reservoir, rebalances it (if needed), and sends it back through the feed lines.
There are two primary ways to build a closed-loop system: single-tank or two-tank setups.
Single-Tank System
Best suited for small tents (up to 120×60 cm or a single plant in 150×150 cm), this setup places the reservoir directly under the plant tray, acting both as the nutrient tank and runoff collection. A submersible pump inside the tank recirculates the solution to the plant.
It’s simple and space-efficient, but flushing the system or adjusting nutrients becomes more difficult because you lack a second clean tank for fresh mixes.
Two-Tank System (Recommended)
For larger setups, a two-tank system offers greater flexibility, control, and safety. Here’s how it works:
- Runoff Collection Tank: Located inside the tent or beneath the grow area, it collects drainage from trays.
- Main Nutrient Reservoir: Typically outside the tent to reduce heat and allow 24/7 access. This tank holds the freshly balanced solution.
- Pumps: One to move runoff from the collection tank to the main reservoir, another to feed plants from the main reservoir.
Each morning (or before the first feed), pump the collected runoff into the main tank, mix thoroughly, test EC / PPM, and rebalance as needed. Then, feed the plants.
Most quality nutrients are pH-stable, but check pH every few days and monitor EC/PPM daily for best results.
The number of pumps and controllers needed depends on your system size. A one-tank setup requires just one pump and Wifi controler. A two-tank system usually requires two pumps and two Wifi controllers for precise scheduling.
Essential Components:
- Emitters (halos, drippers, etc.) suited to your plant density
- Collection trays (e.g., Bucket Company trays or flood tables)
- Return lines for runoff
- Reservoirs for nutrient solution and runoff
- Submersible pumps
- Inline filters (mesh or sediment, ~120–150 micron)
- Controllers (basic timers or smart automation)
- Optional: Nutrient dosing station
Why It’s Perfect for Coco and Perlite
Coco and perlite don’t hold excess nutrients or water well, so you end up feeding often and producing a lot of runoff. That runoff is rarely “waste”—it typically still contains viable nutrients.
A closed-loop system lets you reclaim and reuse it with a simple filtration stage.
Advantages:
- Stable EC and pH (if properly monitored)
- Reduced water and nutrient waste
- Fewer manual tasks (when automated)
- Minimal environmental impact
- Ideal for high-frequency fertigation
- Easier nutrient tracking
Always use buffered coco to prevent calcium and magnesium lockout, especially in recirculating setups.
Example Setup
Here’s how a real-world closed-loop system might look:
- Feed lines use halos or drippers
- Plants sit on raised trays (Bucket Company or DIY containers)
- Drain lines feed into a runoff tank
- Pump #1 moves runoff to the main reservoir
- Pump #2 feeds plants from the main tank
- Optional: Dosing system for nutrient top-up
- Black piping throughout to prevent algae
- Automated controllers handle irrigation timing and system logic
This system runs daily with minimal oversight beyond water top-ups, EC checks, and periodic pH correction.
Management Tips and Warnings
- Nutrient balance can drift over time—replace solution every 7–14 days
- Salt buildup can still occur—flush the medium occasionally with low EC water, and discard that runoff
- Pathogens spread faster in recirculating systems—keep everything clean, and consider UV or beneficial microbes
This system isn’t suitable for organic or soil-based grows, as organic material will degrade and cause system instability.
Final Thoughts
Closed-loop irrigation is a major upgrade for any coco/perlite grower looking for consistency, automation, and efficiency.
It minimizes waste, reduces labor, and gives you tighter control over your grow environment. Once you make the switch, you won’t look back.
If you’re ready to build or upgrade your system, get in touch and we’ll design something tailored to your space and setup.