Fresh water aboard ships has an important role to play for crew, passengers and in cooling of various devices and machines. For that reason, a ship has to be equipped with sufficient amounts of water. Fresh water is obtained by various devices which all have different working methods and principles, such as electrolysis, reverse osmosis, distillation and so on. Vaporizers are devices in which sea water is transformed into fresh water. The produced fresh water is then turned into drinking water with the help of special devices and methods for filtration, bacteriological cleaning and softening. The next step is storing the water into special tanks located on the stern. The size of the vaporizers depends upon the needed amount of water and crew needs. A vaporizer uses an evaporation method so heat energy is crucial for proper functioning. Fresh water produced by fresh water generators is used for drinking, hygienic needs, cooking and even in machines that use fresh water as a refrigerant.