Major institutional reforms are currently under way to improve the performance of the public water sector in Kenya. However, a historical perspective is needed in order to achieve sustainable improvements that will also benefit the urban poor. This article seeks to provide such a perspective, applying a cross-disciplinary and socio-technical approach to urban water supply over the last century, in which institutions, organisations and technology are seen to interact with political, economic and demographic processes. Despite a series of reforms over the years, the socio-technical structure of the urban water sector in Kenya has shown a remarkable stability since the 1920s, and into the 1980s. However, the sustainability of the public service systems has been eroded since independence, due to changes in the institutional framework surrounding the systems, while exclusive standards and technological choices have essentially been preserved from the colonial era. Current sector reform must create incentives for addressing technology choices and service standards in order to provide public water services also for the urban poor.