Increases in water treatment technology have made water recycling a viable engineering solution to water supply limitations. In spite of this, such water recycling schemes have often been halted by lack of public acceptance. Previous studies have captured the public’s attitudes regarding planned reuse schemes, but here we focus on unplanned reuse (i.e. de facto reuse), present in many cities across the U.S. We performed a survey in three metropolitan areas, Atlanta, GA (N = 421), Philadelphia, PA (N = 490), and Phoenix, AZ (N = 418), to assess basic perceptions of treated wastewater occurrence and its acceptance in the public water supply. These perceptions were then coupled by estimates of the actual extent of occurrence in the corresponding cities. The key results are that (1) de facto reuse occurs at rates across the three cities higher than what is perceived; (2) roughly 25% of respondents perceive de facto reuse to occur in their home tap water; and (3) respondents who perceived de facto reuse to occur at their tap were ten times more likely to have a high level of acceptance for de facto reuse in their home tap.