Traditional water indicators primarily focus on water quantity and quality, but emergent research demonstrates that measurement of lived experiences with water availability, accessibility, and use is important for understanding how household water insecurity impacts health and well-being. Few empirical studies have explored which household water insecurity experiences are most salient, or their potential causes, in Latin American cities. We analyzed data from 266 households in a low-income settlement of Cartagena, Colombia, to identify correlates and perceived determinants of water insecurity. The most prevalent household water insecurity experiences were water supply interruptions (96%), water worry (94%), and anger about the water situation (90%). Unexpected water interruptions and use of non-piped primary drinking water sources were associated with greater household water insecurity scores, water worry subscores, and hygiene subscores. Respondents perceived water issues in their community to be caused by deficiencies in gray infrastructure (49%), which included deficiencies in water distribution, treatment, or storage technologies. Social infrastructure (36%), including issues with political, economic, or administrative systems, was also cited as a barrier to water security. We did not detect significant relationships between water insecurity scores and the attribution of these problems to gray or social infrastructure, but there may be relationships between these factors and duration of residency and using a non-piped water source. These findings underscore the importance of socio-political factors and community engagement for improving urban water insecurity through slum-upgrade projects.