A boil water advisory is a public health notice warning residents to boil tap water before drinking, cooking, or brushing teeth due to potential contamination. Advisories may be issued after water main breaks, treatment system failures, flooding, or detection of harmful bacteria like E. coli. Boiling water for at least one minute kills most pathogens, making it safe. Advisories remain in effect until water testing confirms safety, which may take days. Municipalities issue these warnings through multiple channels (media, websites, door-to-door notification) because consuming contaminated water can cause serious illness. Many First Nations communities face long-term boil water advisories due to inadequate water infrastructure.