Climate change and rapid urbanization ask for a radical reconfiguration of the way water is treated and reused. Cities are under particular pressure to develop more flexible, resilient, and modular water management systems. Yet, while many promising experiments with alternative systems exist, they also face considerable challenges. In particular, barriers at an institutional level like existing laws, technology standards or user routines hinder the quick diffusion of new – and potentially more sustainable – UWM solutions. The present project aims at improving our understanding of these barriers and developing new strategies to overcome them based on the experiences from ‘lighthouse cities’ in both developed and emerging economies. Through in-depth mixed methods case studies in San Francisco, Paris and Gothenburg and a structured reinterpretation of existing evidence from Beijing and Bangalore, it will reconstruct the key institutional barriers and drivers that condition the uptake of non-grid-based UWM solutions. It will provide water professionals with a set of interventions to increase the legitimacy of non-grid urban water management options and sketch generic scenarios through which WINGS solutions might diffuse in cities in both developed and emerging economies.