Even in cities where taps are installed in virtually all homes, this is no guarantee of water. The transient character of hydrological landscapes is evident in Mexico City, where water provision is non-permanent in one third of all dwellings. This article investigates hydraulic standby as a form of organizing, exploring modes of standby for water through the lens of anticipation. Sensing and buffering – terms borrowed from cybernetics – are identified as key practices and modes of hydraulic standby that are guided by a logic of precaution and preparedness. While sensing organizes the relation between sensory input and response, buffering refers to the collection of water in anticipation of future shortages. The article draws on 53 individual interviews and other empirical fieldwork conducted in two boroughs of Mexico City. It argues that futures are rendered present in a disparate manner across diverse urban settings, with standby taking on a classed and gendered character.