Urine source separation (NoMix technology) has been proposed as a sustainable alternative to centralized wastewater treatment systems. Radical changes necessitate an early inclusion of sociological expertise, thus offering a real chance fortransdisciplinary collaboration. The practical aim of our survey is to find out how users accept and use existing NoMixtoilets and how this could be encouraged. We collected 1249 questionnaires from 2002 to 2004 in one Swiss school and one Swiss research institute. The technological immaturity of NoMix toilets was noted by many. Nevertheless, acceptance was high: 72% liked the idea and 86% would move into apartments with NoMix toilets. Moreover, most users found that NoMix toilets equal conventional toilets with respect to design (78%), hygiene (84%), and smell (78%). Like many other innovations, the NoMix technology only functions properly if it is used adequately, which we demonstrate for water saving and sitting to urinate. Many users adopted this behavior, e.g., 72% sat. Because perception and use of NoMix toilets is subjective, it can be influenced with certain measures such as good information and cleaning, or discussions with peers. We discuss the importance of social psychology for understanding the factors that influence the acceptance of environmentally friendly innovations.