What is Rainwater Harvesting?
Rainwater harvesting is the sustainable process of collecting and storing rainwater that falls on roof surfaces for later use. Rather than allowing rainfall to run off into storm drains, this water is diverted into storage tanks. It can be used for irrigation, flushing toilets, washing clothes, and even drinking if properly treated.
How to Use the Rainwater Tank Size Calculator
Calculating the ideal tank size involves balancing your harvesting potential with your actual water consumption. To use this tool, follow these steps:
- Roof Surface Area: Measure the footprint of your roof. This is the horizontal area that catches rain.
- Annual Rainfall: Enter the average rainfall for your specific region in millimeters.
- Runoff Coefficient: This factor accounts for water lost to evaporation or absorption by the roofing material. Smooth metal roofs have the highest efficiency.
- Storage Period: Decide how many days of water reserve you want during dry spells.
How is Tank Size Calculated?
The calculation follows a standard formula: Harvest Potential (Liters) = Roof Area × Annual Rainfall × Runoff Coefficient × Filter Efficiency. The recommended tank size is usually calculated based on your daily demand or a percentage of the total annual yield to ensure you have enough water during the driest parts of the year.
Frequently Asked Questions
What is the best material for a rainwater tank? Most residential systems use UV-stabilized polyethylene (plastic), galvanized steel, or concrete. Plastic tanks are lightweight and cost-effective, while steel tanks offer higher durability.
Does the water need filtration? Yes, basic mesh screens are required to keep leaves and debris out. For indoor use, you may need additional sediment filters and UV sterilization.