Here is a little information for those who are considering rainwater harvesting. To keep the water that enters your storage tanks as clean as possible (for potable water), you will want a "first flush system" installed. This system takes the initial water that hits the collection area (your roof) and routes away from your storage tanks.
In order to make sure your roof has been washed clean of various debris, including animal feces, twigs, leaves, pollen, etc., it is recommended that you divert a minimum of 1 US gallon (~3.8 liters) of water for every 100 square feet (~9.3 square meters) of