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Rainwater harvesting collects rooftop rain for garden irrigation, toilet flushing, or other non-potable uses. Collection efficiency is typically 80–90% accounting for losses.

Formel

Harvestable volume (L) = Area (m²) × Rainfall (mm) × Efficiency (0.85 typical)

Trinn-for-trinn guide

  1. 1Harvestable volume (L) = Area (m²) × Rainfall (mm) × Efficiency
  2. 2Efficiency 85% is typical for clean roof with gutters
  3. 3Annual harvest varies greatly by location
  4. 4Tank sized to hold 2–4 weeks of typical use

Løste eksempler

Inndata
80m² roof, 700mm annual rainfall, 85% efficiency
Resultat
Annual harvest = 80 × 0.7 × 0.85 × 1,000 = 47,600 litres

Ofte stilte spørsmål

What is Rain Harvest?

Rainwater harvesting collects rooftop rain for garden irrigation, toilet flushing, or other non-potable uses. Collection efficiency is typically 80–90% accounting for losses

How accurate is the Rain Harvest calculator?

The calculator uses the standard published formula for rain harvest. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Rain Harvest calculator use?

This calculator works with inches, square metres, percentages. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Rain Harvest calculator use?

The core formula is: Harvestable volume (L) = Area (m²) × Rainfall (mm) × Efficiency. Each step in the calculation is shown so you can verify the result manually.

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