1. What is Rainwater Tank Size Calculation?

Rainwater tank size calculation determines the appropriate storage capacity needed for rainwater harvesting systems based on roof catchment area, local rainfall patterns, and runoff efficiency.

2. How Does the Calculator Work?

The calculator uses the rainwater tank size formula:

Where:

• \( V \) — Tank volume (liters)
• \( A \) — Roof catchment area (m²)
• \( R \) — Annual rainfall (mm)
• \( C \) — Runoff coefficient (unitless)

Explanation: The formula calculates the theoretical maximum rainwater collection potential based on catchment area and local rainfall, adjusted for runoff efficiency.

3. Importance of Rainwater Harvesting

Details: Proper rainwater tank sizing is crucial for sustainable water management, reducing municipal water consumption, and ensuring adequate water supply during dry periods.

4. Using the Calculator

Tips: Enter roof area in square meters, annual rainfall in millimeters, and runoff coefficient (typically 0.8-0.9 for clean roofs). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical runoff coefficient value?
A: For clean, impervious roofs, the coefficient is typically 0.8-0.9. For dirty or porous surfaces, it may be lower (0.6-0.7).

Q2: Should I use average or extreme rainfall data?
A: For reliable supply, use average annual rainfall. For drought resilience, consider using drier year rainfall data.

Q3: How does roof material affect collection?
A: Smooth, impervious materials (metal, tile) have higher runoff coefficients than porous materials (thatched, gravel).

Q4: Are there other factors to consider?
A: Yes, consider water demand patterns, dry period duration, and whether the tank will be used as primary or supplementary supply.

Q5: How often should tanks be maintained?
A: Regular maintenance including gutter cleaning, first-flush diversion, and tank inspection should be performed annually.