Posted By Peter Longworth Amjad Legionella can exist in a system where water is chilled, but will remain dormant. At about 20C the bacterium will become active. Legionella enters the body by inhalation, so you need to be able to control the formation of aerosols and mists. If the water is potable then drinking the water should not lead to infection. I'm not sure whether the normal treatment of water for drinking would be adequate to control legionella, maybe someone else can advise on that.