A PWS must notify its customers when it violates drinking water regulations or is providing drinking water that may pose a health risk. Such notifications are provided either immediately, as soon as possible (but within 30 days of the violation) or annually, depending on the health risk associated with the violation. Community water systems—those systems that serve the same people throughout the year—must provide an annual "Consumer Confidence Report" to customers. The report identifies contaminants, if any, in the drinking water and explains the potential health impacts.