Until recently it was believed to be illegal to connect a down spout to a rain barrel in most urban areas in Colorado. Rain barrels are a great way to collect periodic rainfall for garden use – I have three with 40 gallons capacity each. The problem in Colorado was an interpretation of the doctrine of “prior appropriation,” which determines priorities to the use of water. The belief was that rainwater falling on private property would eventually find its way into surface water either directly or via groundwater – and that water might belong to someone with a superior right to it. The problem with this logic is that water from a rain barrel is eventually used to water something, so it will enter the ground just like water from a down spout, so what’s the difference? After much debate the Colorado legislature passed a bill that legalized one or two rain barrels of up to 110 gallons capacity to use on lawns and gardens. Arizona also follows the doctrine of “prior appropriation,” but we never had a controversy about the use of rain barrels in our desert towns and cities. They are a great way to save water and provide non-municipally treated water to your plants.