Household water insecurity is a global threat to human health and development, yet existing metrics lack a systematic consideration of geographic inequality and spatial variation. In this article, we introduce the notion of plumbing poverty as a conceptual and methodological heuristic to examine the intersectional nature of infrastructure, space, and social inequality. Plumbing poverty is understood in a dual sense: first, as a material and infrastructural condition produced by social relations that fundamentally vary through space and, second, as a methodology that operationalizes the spatial exploration of social inequality. Drawing on millions of census records, we strip household water security down to a single vital measure—the presence of complete household plumbing—to assess its spatial and sociodemographic trends. We identify distinct hot spots (geographic clusters of higher than average values) of plumbing poverty, track its social and spatial variance, and expose its fundamentally racialized nature. Our study finds that plumbing poverty is neither spatially nor socially random in the United States. Rather, plumbing incompleteness is spatially clustered in certain regions of the country and is clearly racialized: Living in an American Indian or Alaskan Native, black, or Hispanic household increases the odds of being plumbing poor, and these predictors warp and woof through space. In considering who experiences the slow violence of infrastructural dysfunction, a geography that is simultaneously ignored and unevenly expressed in the United States, we argue that analyses of space and social difference are central to understanding household water insecurity and must be prioritized in the development of cross-comparable metrics and global measurement tools. Key Words: census microdata, hot spot analysis, household water insecurity, infrastructural geographies, IPUMS.