Health officials often lack information about characteristics that predict which water systems are most likely to be placed on and to persist on drinking water advisories (e.g. health warnings offering advice or information). This study uses data collected by the Interior Health Authority in British Columbia to characterize water systems on advisory for microbiological threats and to identify the variables associated with advisory status and length. By systematically extracting key characteristics, this study explores advisory status by examining associated variables: water systems size, administrative area, governance structure, water source, treatment level, and service type (e.g. residential or commercial systems). Results show residential and commercial water systems have different characteristics associated with advisory status and length. For residential systems, certain governance structures are more likely to be placed on and to stay on advisory, especially the cooperative governance structures not operated by local governments. For commercial systems, administrative area and system size were associated with advisory status, but not advisory length. The overall results highlight the influence of governance structure and support the need for targeted interventions to improve residential small water systems not operated by local governments or utilities. Lastly, these results show how health officials can use administrative data for program planning and evaluation.