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Hydroponic Nutrient Water Needs Estimator

The Hydroponic Nutrient Water Needs Estimator calculates make-up water required by a recirculating hydroponic system over a selected period. It combines plant water demand, the share of that demand recovered back into the system, and additional daily system losses such as leaks, cleaning draw-off, or non-recovered evaporation that you choose to include.

This model is most useful for reservoir sizing, top-up planning, and comparing crop scenarios where a known liters-per-plant-per-day demand is available. The recovery percentage represents water that returns to the recirculating loop instead of needing replacement. Plant uptake itself is generally not recoverable, so users should set the recovery value to match how their underlying demand figure was defined. Actual water use can vary sharply with crop stage, temperature, humidity, light, airflow, and sanitation practices; the estimator therefore scales your assumptions rather than prescribing a universal hydroponic water requirement.

Water-use assumptions

plants
L/plant/day
days
%
L/day
Result
—
make-up water required
Gross plant-system demand—
Recovered water—
Other losses—
Average make-up per day—

1. Enter plant sites
Use the number of active plants represented by the water-demand assumption.

2. Set gross water demand
Enter liters per plant per day for the crop and production stage you want to model.

3. Choose the planning period
Enter the number of days for reservoir top-up or supply planning.

4. Enter the recovered share
Use the portion of the gross demand that returns to the loop and can be reused under your chosen definition.

5. Add other daily losses
Include known non-recovered water such as drain-off, leaks, or cleaning losses if they are not already in the demand figure.

6. Review make-up volume
The result shows total replacement water and the average amount required per day.

Gross demand = Plant sites × L/plant/day × Days Recovered water = Gross demand × (Recovery % ÷ 100) Make-up water = Gross demand − Recovered water + (Other loss/day × Days)

What the result means

The result is the estimated fresh water that must be added during the planning period to replace modeled non-recovered demand and other losses.

Avoid double-counting losses. If your liters-per-plant figure already represents net make-up water, set recovery to 0% and include only separate losses not embedded in that figure.

Given: 750 plants, 1.6 L/plant/day gross demand, 28 days, 15% recovery, and 20 L/day of other losses.

Calculation: Gross demand = 750 × 1.6 × 28 = 33,600 L. Recovered = 33,600 × 0.15 = 5,040 L. Other losses = 20 × 28 = 560 L. Make-up = 33,600 − 5,040 + 560 = 29,120 L.

Result: About 29,120 L of make-up water.

That is an average of 1,040 L per day for the selected period.

Is plant uptake considered recoverable water?

Usually no. Water incorporated into plant tissue or transpired out of the system is not returned to the reservoir. Set recovery according to how your gross demand figure was measured or defined.

Should nutrient-solution changes be included as other losses?

Yes, if discarded solution is replaced with fresh water and that volume is not already included in your demand figure. Enter an average daily equivalent for the planning period.

Can I use gallons instead of liters?

The interface is labeled in liters. Convert gallons to liters before entering values if you want the result to remain correctly labeled.

Why can measured top-up differ from the estimate?

Water demand changes with crop size, vapor-pressure conditions, light, airflow, leaks, maintenance, and irrigation scheduling. Use measured top-up data to refine the assumptions over time.

How is this different from a nutrient rate calculator?

Water needs estimate replacement volume. A nutrient rate calculator determines how much nutrient material is associated with a target solution concentration or application rate.