In the late nineteenth century, Sulina, a settlement of about 10,000 inhabitants, was Romania’s busiest port. Located at the mouth of the only navigable branch of the Danube, the town held a strategic position along South-Eastern European transportation corridors, being the gateway of Lower Danubian trade and shipping. But Sulina was also a hydrobiological melting pot of natural and anthropogenic water flows carried by the Danube, the Black Sea’s currents, and the tanks and bilges of the thousands of ships that came to load their cargoes in the local harbour and roadstead. With advances in the science of bacteriology, provisioning Sulina with safe urban water became a Romanian and international public health priority. Investments in the town’s water supply and sanitation are a fascinating, yet little-known episode of sanitary internationalism, in which several actors in Romania and Europe cooperated – institutionally, technologically and financially – in the attempt to bring sanitary civilisation to one of Europe’s most crucial commercial and epidemiological gateways. In line with similar interest for water, disease and urban infrastructure in a peripheral (quasi-colonial) context, this paper will be illustrative for the growing debates in Romania around the quality of water in the context of the larger hygiene movement. The rhetoric of ‘improvement’ and ‘progress’ in providing access to safe drinking water, stemming from the idea that ‘uncleanliness with all its consequences comes mainly from lack of water’, was accompanied by calls for the construction of modern water infrastructure.