The primary purpose of a rain barrel is to provide homeowners and gardeners a source of soft, slightly acid water that is typically preferable to well water (which may have excessive mineral content) for irrigating woody and herbaceous ornamentals, as well as lawns. Rain barrels can also reduce the potential for basement flooding by directing water away from house foundations. In addition, rain barrels reduce the amount of water running into lakes and rivers, thus reducing erosion and helping prevent storm water pollution of lakes and waterways. Rain barrels work particularly well on smaller properties where plants can be watered directly from a barrel using an attached hose. Due to possible leaching of chemicals and microorganisms (e.g., bacteria and fungi) from roofing materials, rain barrel water is not recommended for use on vegetables, or for human consumption. Rain barrels are not recommended for homes with tar and gravel roofs, or roofs made of asbestos or treated cedar shakes shingles.
You can purchase (relatively inexpensively) rain barrel kits which will give you everything you need to get started, but there are very few (if any) restrictions as to the materials to use and the size of the barrel. Many of us may already have what is needed to put together a great system. Please do some research, a simple google search, and see how easy it is to get started.
Rain barrels should be installed only on level surfaces and elevated using concrete or cinder blocks, or a sturdy wooden stand. Elevating a rain barrel helps to increase pressure, and thus flow when emptying the barrel. Barrels must have a secure base to prevent tipping. Fifty gallons of water weigh several hundred pounds, and may be a risk to children if they try to climb on the barrel and the barrel tips. For more information, please visit the UW-Extension Website.