Sizing a stormwater tank involves estimating how much runoff can be captured and how much water is needed for its intended use. The process begins by calculating the catchment area, such as a roof or paved surface, and multiplying it by the average rainfall and a runoff coefficient, which reflects how much water actually flows off the surface rather than being absorbed. This gives an estimate of the total volume of water that can be collected during a typical storm event.
The tank size should also consider how frequently it rains, how much water will be used between storms, and whether the system is designed to capture all runoff or just a portion. In some cases, local regulations or design standards may dictate minimum storage requirements or provide guidelines based on storm return periods, such as a 1-in-10-year event. It's important to balance the tank’s capacity with space constraints, budget, and overflow management, ensuring it is large enough to be effective without being unnecessarily oversized.
