Concerns about aging infrastructure, pressure on water supplies, and increasingly stringent wastewater discharge regulations have led water providers to consider new and innovative approaches. One such approach involves the distribution of reclaimed water through a dual distribution system in which the piping is separated into two separate and independent networks. One network is used exclusively for potable water, the other for non-potable water. This paper summarizes the results of a recently completed study sponsored by the Water Research Foundation in which a retrospective assessment of the performance of existing dual water systems was performed. Criteria for the performance assessment were established through an extensive literature review, the development of 37 case studies, site visits, feedback from workshop participants, and the creation of a classification framework that enables comparisons among similar dual systems. The study concluded that the primary motivators in using dual systems are to extend water supplies and provide more options for wastewater management. While dual systems can provide benefits such as extending the lives of existing potable water systems and deducing risk from drought, there are many issues such as storage for non-potable supplies, rate-setting, and true costs accounting that remain to be resolved.