Rain Barrel Guide
This link explains some products on the market to harvest rain water. It provides calculations on how much rain water can be harvested from a roofs catchment area.
Harvesting systems can vary from the simple use of barrels aided by the force of gravity to deliver the water, to more advanced systems using cisterns, pumps, and flow controls. There are a few things you can do to find out what kind of rainwater harvesting system is right for you. The information presented in the rest of this website consists of a few simple steps to help you learn about rainwater collection before you buy a rain barrel or water harvesting system.
Green Buildings (LEED), Stormwater Management, Water Quality/Quantity