Water safety plans are public health related risk management plans, covering the entire water supply system, based on the theorem of prevention. Risk evaluation is fundamental for setting up a risk management system. A modified risk assessment equation is shown which takes into account the severity of consequences of the hazard an accentuated way. This method was used successfully n a number of practical water safety system applications. Water safety plans are practical tools for water utility operators which can be applied in different fields of operation, from water quality improvement of decision support tool of developments. The role of the distribution system and its operation is clarified from water quality deterioration and risk mitigation point of view.