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Rainwater Tank Size Equation:
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The rainwater tank size equation calculates the optimal tank volume based on roof catchment area, annual rainfall, runoff coefficient, and system efficiency. It helps determine the appropriate tank size for rainwater harvesting systems.
The calculator uses the rainwater tank size equation:
Where:
Explanation: The equation calculates the total volume of rainwater that can be collected from a roof area considering rainfall patterns, runoff efficiency, and system losses.
Details: Proper tank sizing is crucial for optimizing rainwater harvesting systems. An appropriately sized tank ensures adequate water supply while avoiding unnecessary costs for oversized tanks.
Tips: Enter roof area in square meters, annual rainfall in millimeters, runoff coefficient (typically 0.8-0.95 for roof surfaces), and system efficiency (typically 0.7-0.9). All values must be positive numbers.
Q1: What is a typical runoff coefficient for roofs?
A: Runoff coefficients typically range from 0.8-0.95 for most roof materials, with smoother surfaces having higher coefficients.
Q2: How is system efficiency determined?
A: System efficiency accounts for losses from evaporation, first flush diversion, overflow, and filtration, typically ranging from 0.7-0.9.
Q3: Should I use average or extreme rainfall data?
A: For reliable water supply, use average annual rainfall. For drought resilience, consider using lower percentile rainfall data.
Q4: Does roof material affect the calculation?
A: Yes, different roof materials have different runoff coefficients. Metal roofs typically have higher coefficients than tile roofs.
Q5: How often should the tank be sized?
A: Tank sizing should be reviewed if rainfall patterns change significantly or if water demand patterns are altered.