The average roof sheds 160 gallons of rainwater per hour during a moderate rain fall. Rainwater is better for your garden than tap water: it is at ambient temperature rather than being cold, and it is not chlorinated or treated with chemicals.
The Garden Water Saver, is a device that attaches to your home’s downspout, and allows you to use any container as a rainwater barrel. It diverts rainwater until the container becomes full, and then it automatically shuts off. It will fill a 55 gallon rain barrel in 2 to 3 hours during a moderate rainfall. The kit is available for $19.95 from Garden Water Saver.