Even builders itching to try out a graywater recycling or rainwater harvesting system on their next project may find they need to wait a bit longer: In many states, the practices are still not allowed by code. In fact, only seven states currently allow the use of both conservation methods, although some local jurisdictions allow them.

The map above provides a breakdown of where state-level legislation permits using graywater and/or rainwater harvesting systems. However, this is only a surface-level representation; in fact, codes and regulations for these programs are varied and complex. For example, some states will permit rainwater harvesting only for nonpotable use, while others allow it to be filtered to drinking water. And in many states, graywater use is permitted only for certain types of homes or applications.

Standards are evolving quickly, so for the most up-to-date and specific permitting information for your area, always refer to your local regulatory agency.