Throughout the world, rainwater harvesting is a way of life; and in the U.S., it is rapidly growing in popularity as a simple and easy conservation method. Drought, limited resources and energy costs are driving the trend for rainwater harvesting based on the fact that about 70% of the water we use can be replaced with rainwater. Rainwater harvesting systems collect and use the water at the source, reducing energy needs for processing and movement as well as limiting storm water run-off.