In order to understand how much rainwater can be captured you need to know the surface area of the building or structure that will be used to capture the rainwater. By using the average annual rainfall data in your area you can calculate how much water will be captured during an average rain season.

This will give you an indication of how much water you can capture and how big your storage tank should be. The storage tank is one of the more expensive components to a system. We have found many systems that have too little storage capacity and lose a lot of potential water.