Flush Schedule Calculator

Choose your medium, pot size, and feeding strength. Get routine flush dates and water volumes. Stay ahead of buildup with simple, practical guidance weekly.

Flush Schedule Calculator
Use the form below, then submit to get a schedule.
Changes pot/reservoir display units.
Affects final flush timing suggestion.
Used only when crop preset is Custom.
Controls base interval and volume factor.
Ignored for hydro; use reservoir volume instead.
Used only when medium is hydro/reservoir.
More frequent feeds often need more frequent flushes.
Use 0 for plain water schedules.
If blank/0, buildup is estimated from LF.
Higher EC water increases salt load over time.
Typical container targets: 0.10–0.20.
Higher temps can concentrate salts faster.
High risk shortens recommended interval.
Used to calculate your next routine flush date.
Used to compute a calendar start for final flush.
Helps phrase final flush timing in days remaining.
Reset
Example Data Table
Sample inputs and typical outputs for reference.
Crop Medium Container Feed EC Runoff EC Interval Flush volume
Fruiting Coco 10 L 1.8 2.2 12 days 27.00 L
Leafy greens Soil 15 L 1.2 1.3 20 days 30.00 L
Herbs Hydro 40 L 1.6 — 7 days 40–60 L
Actual needs change with cultivar, airflow, and irrigation style.
Formula Used
How the calculator estimates timing and volume.
1) Salt buildup ratio

When runoff EC is provided, buildup is measured as:

Buildup ratio = Runoff EC ÷ Feed EC

Higher ratios shorten the flush interval and raise flush volume.

2) Interval estimation

A base interval is chosen by medium, then adjusted:

Interval = Base × Frequency × Buildup × Risk × Temp × Water × Size

The result is clamped to 3–45 days for practicality.

3) Leaching requirement

A conservative minimum leach fraction estimate is:

LR = ECw ÷ (5×ECt − ECw)

ECw is source water EC; ECt is a tolerable root-zone EC estimate.

4) Flush volume

A medium-based volume factor is increased with buildup:

Flush volume = Container liters × Volume factor

For hydro, the factor represents drain-and-refill cycles.

How to Use This Calculator
A simple workflow for better decisions.
  1. Select your medium and crop preset first.
  2. Enter pot size (or reservoir volume for hydro).
  3. Add feeding and runoff EC if you measure it.
  4. Set a realistic leach fraction and your temperature.
  5. Submit to see interval, volume, and final flush timing.
  6. Download CSV or PDF to keep a grow log.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.