Home
Back
Rainwater Tank Capacity Formula:
| From: | To: |
The rainwater tank capacity formula calculates the potential volume of rainwater that can be collected from a catchment area. It considers the catchment area, rainfall amount, and runoff coefficient to estimate tank capacity in gallons.
The calculator uses the rainwater tank capacity formula:
Where:
Explanation: The formula calculates the volume of rainwater that can be harvested from a specific catchment area during a rainfall event, accounting for losses through the runoff coefficient.
Details: Rainwater harvesting is crucial for water conservation, reducing dependence on municipal water supplies, and providing an alternative water source for irrigation, flushing toilets, and other non-potable uses.
Tips: Enter catchment area in square feet, rainfall in inches, and runoff coefficient (typically 0.8 for roofs, 0.3-0.5 for lawns). All values must be valid positive numbers.
Q1: What is a runoff coefficient?
A: The runoff coefficient represents the percentage of rainfall that becomes available runoff. It ranges from 0 to 1, with impervious surfaces having higher values.
Q2: Why is the conversion factor 0.623?
A: This factor converts cubic feet to gallons (1 cubic foot = 7.48 gallons) and inches to feet (1/12), resulting in 7.48/12 = 0.623.
Q3: What are typical runoff coefficients?
A: Roofs: 0.8-0.95, Pavement: 0.7-0.95, Lawns: 0.05-0.35, Forest: 0.01-0.20 depending on soil type and slope.
Q4: How accurate is this calculation?
A: It provides a reasonable estimate but actual collection may vary due to evaporation, first flush diversion, and system efficiency.
Q5: Can this water be used for drinking?
A: Not without proper filtration and treatment. Rainwater may contain contaminants from the catchment surface and atmosphere.