Rainwater Harvesting & Tank SizingEngineering

Rainwater Harvesting Catchment Volume & Storage Cistern Tank Calculator

Calculate harvestable rainwater runoff volume in Liters and Cubic Meters (m³), first-flush diversion, and optimal underground storage cistern tank sizing.

Calculator Inputs

Live Real-Time
Quick select:
mm
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Calculated ResultRainwater Harvesting & Tank Sizing

Total Annual Harvestable Water (m³)

59.85

Annual Water Harvested (Liters)

59,850 L

Recommended Cistern Tank Size (m³)

14.96 m³

Recommended Tank Size (Liters)

14,962.5 L

Sustainable Water Security: Rainwater catchment yields substantial cost-free municipal water savings.

Rainwater Yield & Storage

Cistern Tank (m³)
14.96 m³(20%)
Total Harvest (m³)
59.85 m³(80%)

Detailed Calculation Breakdown

Cistern Tank (m³)
14.96 m³
Total Harvest (m³)
59.85 m³

Calculation Methodology

Harvested Volume (Liters) = Roof Area (m²) * Rainfall (mm) * Runoff Coefficient C * 0.95 (First Flush Efficiency). Cubic Meters = Liters / 1000. Recommended Cistern Size = Annual Yield * 0.25.

Important Legal & Educational Disclaimer

This environmental and hydrological engineering tool models building rainwater collection systems.

This calculator is designed for educational and informational purposes only based on public statutory frameworks. The outputs do not constitute binding financial, tax, or legal advice. We assume no liability for decisions made based on these estimations. Always verify with the relevant official authorities or a certified professional advisor.

Frequently Asked Questions

Smooth metal and asphalt/concrete roofs have C ≈ 0.90 to 0.95; clay tiles have C ≈ 0.80 to 0.85; green turf roofs have C ≈ 0.30 to 0.50.
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