This paper aims to explain the process of change and modernisation that experienced Spanish cities in the period between 1870 and 1936. This profound transformation was in the demolition of old walls and the route of the new ensanches, the arrival of the railway, the development of new means of transport as the tram or the installation of electricity grids and gas. These new economic sectors have been very studied from different points of view. Conversely, a new sector such as water in which economic, legal, urban and ecological interests converge has gone unnoticed through the modern historiography. The implementation of networks at home supply demanded agglutinate public and private interests and can serve as indicator showing the degree of modernization of Spanish cities.
Keywords: Spain; Modernisation; Fresh water supply firms; public service; Local government; City