Fresh Water Generator

A fresh water generator produces potable or technical water by distilling seawater using waste heat from the main engine jacket cooling water circuit, which exits the engine at around 80–90 °C. The seawater feed is introduced into a low-pressure evaporator where reduced absolute pressure lowers the boiling point to around 40–55 °C, allowing evaporation without additional fuel consumption. The vapour is then condensed and the distillate passed through a salinity electrode that monitors conductivity; if salinity exceeds the set limit the distillate is automatically dumped overboard rather than stored. Fresh water generators are typically run only when the vessel is more than a defined distance offshore — commonly at least 12 nautical miles from land — to avoid contamination from coastal waters. The output depends on engine load and sea temperature: a standard unit may produce between 20 and 30 tonnes per day. Water produced is stored in a potable water tank, treated with a chlorination or UV system, and recorded in the deck or engine-room log. Maintenance involves periodic de-scaling of the evaporator plates and renewal of the zinc anodes protecting the aluminium evaporator body.