How to Calculate Rainwater Harvesting
What is Rainwater Harvesting?
Rainwater harvesting collects rooftop rain for garden irrigation, toilet flushing, or other non-potable uses. Collection efficiency is typically 80–90% accounting for losses.
Formula
Step-by-Step Guide
- 1Harvestable volume (L) = Area (m²) × Rainfall (mm) × Efficiency
- 2Efficiency 85% is typical for clean roof with gutters
- 3Annual harvest varies greatly by location
- 4Tank sized to hold 2–4 weeks of typical use
Worked Examples
Frequently Asked Questions
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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