# Drain-to-waste

> Drain-to-waste fertigation feeds each plant fresh nutrient solution and lets the runoff leave the system rather than returning it to the reservoir.

- Canonical: https://genetixbay.com/knowledge/glossary/drain-to-waste.html
- Also written: drain to waste, DTW, run to waste, open system, free-draining fertigation
- 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"

Drain-to-waste (an open system) is a [fertigation](https://genetixbay.com/knowledge/glossary/fertigation.md) method in which every irrigation is fresh, [pH-](https://genetixbay.com/knowledge/glossary/ph-down.md) and EC-adjusted solution, and whatever [drains](https://genetixbay.com/knowledge/glossary/runoff.md) from the pot goes to a drain or collection tank and is not reused. It is the standard method for [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md) and rockwool, both commercially and in many home grows.

## In practice

Because the plant always sees a known solution, drain-to-waste is stable and easy to diagnose. Growers monitor runoff volume (often 10-20% of input), runoff [EC](https://genetixbay.com/knowledge/glossary/ec.md) and runoff [pH](https://genetixbay.com/knowledge/glossary/ph.md) to see what is happening in the medium. It pairs naturally with crop steering, where the size and timing of irrigations are adjusted to push vegetative or generative growth. The cost is more water and nutrient use than a [recirculating system](https://genetixbay.com/knowledge/glossary/recirculating-system.md) and the need to dispose of runoff responsibly.

## Don't confuse with

- **Recirculating (closed)**: solution returns to the reservoir and is reused.
- **Hand watering to runoff**: the same principle done manually in soil or coco.

## Related terms

[Recirculating system](https://genetixbay.com/knowledge/glossary/recirculating-system.md), [Drip irrigation](https://genetixbay.com/knowledge/glossary/drip-irrigation.md), [Crop steering](https://genetixbay.com/knowledge/glossary/crop-steering.md), [Watering to runoff](https://genetixbay.com/knowledge/glossary/watering-to-runoff.md), [Dryback](https://genetixbay.com/knowledge/glossary/dryback.md)

## Read more

- [Drain-to-waste drip and crop steering (generative vs vegetative dryback)](https://genetixbay.com/knowledge/systems/drain-to-waste-crop-steering.md)
- [Runoff testing: how to measure root-zone pH and EC and what the numbers mean](https://genetixbay.com/knowledge/ph-ec/runoff-testing.md)

## Sources

1. Raviv M, Lieth JH, Bar-Tal A (eds), 2019. Soilless Culture: Theory and Practice, 2nd ed. Elsevier. https://doi.org/10.1016/C2015-0-01807-5
2. Stemeroff J, 2018. Irrigation management strategies for medical cannabis in controlled environments. MSc thesis, University of Guelph. http://hdl.handle.net/10214/12125