This document discusses approaches for managing risks from Legionella in potable water systems and cooling towers. It notes that biofilm formation and stagnant or slow moving water increase risks. Multiple barriers like disinfectants, filtration and maintenance plans are recommended, but zero risk does not exist and risks differ between potable water and cooling towers. Lessons from a 2012 Quebec outbreak highlight the need for thorough cleaning before disinfection and validating biocide dosing. The Quebec law requires documentation and maintenance plans to be signed by professionals. Increased water consumption or switching to air cooling can occur when risks are difficult to control. District cooling systems avoid Legionella risk and reduce energy use.