A part of the Ottoman Empire for centuries, the city of Ioannina integrated into the Greek state following the Balkan wars of 1912–13. This article provides a first in-depth historical account of the city's water supply system from the early 1910s to the eve of World War II, and traces the path leading from a traditional system relying on private wells and public fountains to a modern water network entering inhabitants’ homes. In doing so, it also offers material and insights contributing to a larger research project on the technological modernization of urban Greece in the inter-war period, during which the Greek state itself was driven by a particularly strong urge to modernize the country.