The best answer I can find is that you multiply the square footage of your roof area by .623. This gives you the gallons per inch of rainfall. I have found numbers ranging from .5 to .75 but the .623 is the most consistent.
Rooftop Rain Water Harvesting is the technique through which rain water is captured from the roof catchments and stored in reservoirs. Harvested rain water can be stored in sub-surface ground water...
Depending on where you live, it could range from 90% to 70% or even lower. Rain water can consist of pollution if business plants are near by. The majority of store bought water will always be...
is a http://wiki.answers.com/wiki/Water_tank which is used to collect and store rain water http://wiki.answers.com/wiki/Surface_runoff, typically from http://wiki.answers.com/wiki/Rooftop via...