Access to hygiene services remains one of the most urgent challenges facing countries, especially low-income ones. This has become much more critical in the current context of the COVID-19 pandemic. The WHO/UNICEF Joint Monitoring Program globally monitors access to hygiene service levels. As data are in three parts with a constant sum and a positive value, they are compositional data. Inequality is monitored in disaggregated data; in the urban–rural case, this is done through a simple difference between the urban and rural service levels. However, this simple form of calculation does not take into account the characteristics of the data, which can lead to erroneous interpretations of the results. Therefore, we propose an alternative measure of inequality that uses a ternary diagram and does not infringe on the data properties. The results of the new urban–rural inequality measure show spatial heterogeneity. The highest inequality occurs in Colombia, with a value of 37.1 percentage points, and the lowest in Turkmenistan, with a value of zero. Our results also show that 73 of the 76 countries evaluated have higher basic hygiene services in urban areas than in rural areas. This means that urban households have more availability of a handwashing facility on-premises with soap and water than rural households. Likewise, by subdividing the ternary diagram into ternary parcels, we could group and rank the countries based on hygiene service conditions in a hierarchical order using tripartite information. Finally, our study finds that a multivariate measure of inequality can be important for the public policies of the sector with a general vision, which underscores the value of making evidence-based decisions.