Cities in the Global South are generally vast due to urban sprawl. They are characterised by a varying level of density, and enclaves of informal settlements. Within this context, this article addresses the limits of large-scale and centralised water systems. It seeks to understand, qualitatively, to what extent the decentralised approach to water management has been adopted within the current development practises in the Southeast Asia region. The case studies in Jakarta, Indonesia, and Soc Trang, Viet Nam, show that by "scaling down" the development interventions, the socio-spatial characteristics of local communities can be accommodated. Smaller-scale development intervention also means stimulating creativity in planning and policy-making processes to address water-infrastructure needs at local levels and opens possibilities for integrating water-infrastructures with public space. Such a decentralised approach matters to improve the overall socio-spatial quality of a neighbourhood, however it requires, in parallel, new institutional mechanisms to provide a coherent water and environmental management system at the urban level. This article argues for a synergy of two axes: the water sector as a crucial development sector, and the neighbourhood as a vital scalar dimension. This synergy is a strategic step to improve the overall quality of urban life.