Greywater Irrigation Sizing Calculator

Plan a safe greywater irrigation system by matching available volume, landscape demand, and distribution capacity with configurable buffers.

Litres collected from showers, laundry, and sinks each day
Total landscape area fed by the greywater system
Water depth required by the plants each week
Number of scheduled irrigation days during the week
Optional: storage window before use; defaults to 24 hours when blank
Optional: flow rate through drip lines or emitters (defaults to 20 L/min if blank)
Optional: filtration size to protect emitters (defaults to 1 mm)

Planning reference only. Verify plumbing codes, backflow prevention, and water quality standards in your jurisdiction before installing a greywater system.

Examples

  • 280 L/day supply, 35 m² beds, 5 L/m²/week, 3 irrigation days, 18 h storage, 12 L/min flow ⇒ Weekly deliverable volume: 175.00 L (surplus of 1,785.00 L). Suggested equalisation tank: 43.75 L. Run time per irrigation day: 4.86 minutes at 12.00 L/min. Recommended filter mesh: 1.00 mm.
  • 210 L/day supply, 24 m² orchard, 7 L/m²/week, 2 irrigation days, default storage, 15 L/min flow, 0.8 mm filter ⇒ Weekly deliverable volume: 168.00 L (surplus of 1,302.00 L). Suggested equalisation tank: 84.00 L. Run time per irrigation day: 5.60 minutes at 15.00 L/min. Recommended filter mesh: 0.80 mm.

FAQ

What happens if I leave the optional fields blank?

The calculator assumes a 24-hour storage window, 20 L/min distribution flow, and 1 mm filtration when optional values are omitted, so the results stay conservative.

How should I choose the application rate?

Base it on plant water demand or evapotranspiration charts for your climate. Increasing the rate shows how much additional potable water you may need.

Can I model multiple irrigation zones?

Run the calculator separately for each zone or sum their areas and use the highest application rate to confirm the combined system stays within supply.

Why is the deliverable volume lower than my weekly supply?

When landscape demand is below the available greywater, the model caps delivery at the demand to avoid over-irrigation that could breach regulations.

Additional Information

  • Result unit: liters per week applied to the landscape.
  • Equalisation storage defaults to 24 hours, aligning with hygiene guidelines that discourage holding greywater longer than one day.
  • Flow rate input helps estimate runtime per irrigation event for valve and controller sizing.
  • Filtration recommendations assume coarse screening; tighten the mesh for drip emitters smaller than 1 mm.

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