Urban water management policy in Japan, with examples from Fukuoka city, is described and the potential for sustainability of Fukuoka's urban water system is discussed. A framework of the qualitative characteristics of a sustainable system (including social, environmental and economic factors) is developed and used in the analyses presented here. The Fukuoka example shows that technically advanced solutions for use of reclaimed water and rainwater in buildings can be practically and economically feasible. Regarding the organization it is shown that the wastewater sector has a somewhat lower status than the water sector. It is argued that merging the water and wastewater sectors could stimulate the development of a holistic approach to urban water management, contribute to increasing resources availability for the wastewater sector and, in this way, the overall sustainability of the urban water system. Tackling water shortages through controlling water demand, investments in increasing water distribution efficiency and utilization of reclaimed water and rainwater in Fukuoka are all in line with increasing sustainability of the urban water system.