# Recirculating system

> A recirculating (closed) system returns drained nutrient solution to the reservoir to be reused, saving water and nutrients but needing more monitoring and sanitation.

- Canonical: https://genetixbay.com/knowledge/glossary/recirculating-system.html
- Also written: recirculating, recirculating hydro, closed system, closed-loop hydroponics, recirc
- Glossary category: Systems and media · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

A recirculating hydroponic system collects the solution that passes through or around the roots and returns it to the reservoir. [DWC](https://genetixbay.com/knowledge/glossary/dwc.md), [RDWC](https://genetixbay.com/knowledge/glossary/rdwc.md), NFT, [ebb and flow](https://genetixbay.com/knowledge/glossary/ebb-and-flow.md) and recirculating drip are all closed systems. Only what the plants take up or evaporate is lost, so water and fertiliser use falls sharply compared with [drain-to-waste](https://genetixbay.com/knowledge/glossary/drain-to-waste.md).

## In practice

Because solution is reused, its composition drifts: the plant takes some elements faster than others, [pH](https://genetixbay.com/knowledge/glossary/ph.md) moves, and root exudates and microbes accumulate. Growers top up between full changes, check pH and [EC](https://genetixbay.com/knowledge/glossary/ec.md) daily, and change or refresh the reservoir every one to two weeks. Recirculation can spread root pathogens such as *[Pythium](https://genetixbay.com/knowledge/glossary/pythium.md)* to every plant, so sanitation, cool temperatures and a deliberate microbial strategy (beneficial or sterile) matter.

## Don't confuse with

- **Drain-to-waste**: each feed used once.
- **Recirculating drip**: one kind of closed system using [drippers](https://genetixbay.com/knowledge/glossary/drip-irrigation.md).

## Related terms

[Drain-to-waste](https://genetixbay.com/knowledge/glossary/drain-to-waste.md), [Reservoir](https://genetixbay.com/knowledge/glossary/reservoir.md), [RDWC](https://genetixbay.com/knowledge/glossary/rdwc.md), [NFT](https://genetixbay.com/knowledge/glossary/nft.md), [Ebb and flow](https://genetixbay.com/knowledge/glossary/ebb-and-flow.md)

## Read more

- [Recirculating drip (top-feed, runoff returns)](https://genetixbay.com/knowledge/systems/recirculating-drip.md)
- [Choosing your growing system: soil, coco, rockwool or hydro](https://genetixbay.com/knowledge/systems/choosing-a-system.md)

## Sources

1. Resh HM, 2022. Hydroponic Food Production, 8th ed. CRC Press. https://doi.org/10.1201/9781003133254
2. Colorado State University Extension PlantTalk 2043. Root disease problems and management in hydroponic systems. https://planttalk.colostate.edu/topics/miscellaneous/2043-root-disease-problems-management-hydroponic-systems/