Drain-to-waste (an open system) is a fertigation method in which every irrigation is fresh, pH- and EC-adjusted solution, and whatever drains from the pot goes to a drain or collection tank and is not reused. It is the standard method for coco 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 and runoff pH 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 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.
Fertigation is delivering fertiliser dissolved in irrigation water, so plants are fed every time they are watered rather than through solid amendments.pH Down is any acid used to lower solution pH, commonly phosphoric, nitric or sulfuric acid; each adds a nutrient, and all need gloves and eye protection.Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.A recirculating (closed) system returns drained nutrient solution to the reservoir to be reused, saving water and nutrients but needing more monitoring and sanitation.Watering to runoff means applying enough water or solution that some drains from the bottom of the container, typically 10-20% of the volume applied.Drip irrigation delivers water or nutrient solution through tubing and emitters directly to each plant's medium, in measured amounts on a timer or controller.Crop steering adjusts irrigation timing, volume and dryback, along with climate, to push plants towards vegetative growth or generative (flowering) growth.Dryback is the drop in a substrate's water content between irrigations, usually expressed as a percentage of its content at full saturation.
