There is an urban legend that colleting rainwater on your own property is illegal in many states. The reality is that, yes, in about a dozen states, it is against the law. But you have to read the laws carefully to understand that it doesn't apply to small-scale collection at home. The laws simply require water rights permits when it comes to using public water supplies (like waterways), or when it becomes water collection that's done on a massive scale. But if you have a rainwater collection system that simply collects water for your own property use, not only is it perfectly fine, you may be eligible for tax credits for installing such a system.