FAQ / Support Center

All of the piped water supplied on Grand Cayman, including Cayman Water supplied water is desalinated water. That is, raw water with the same amount of salt in it as seawater is treated using a process called reverse osmosis. Reverse Osmosis separates the salt from the water leaving fresh water that is further treated to finished potable water quality and distributed to our customers.

Cayman Water piped water contains approximately 100 milligrams (mg) of sodium per liter of water. There are various recommendations for the limit of daily sodium intake, with the average being around 2000 mg. Drinking half a liter of tap water a day would provide approximately 2.5% of your recommended daily intake of sodium. For comparison, a typical cheeseburger contains almost 1500 mg of sodium, 75% of the recommended daily intake.

Cayman Water is required under the water quality regulations contained in its License Agreement, and regulated by Water Authority-Cayman, to maintain a free chlorine residual in water supplied to our customers. The amount of chlorine added must maintain an average of approximately 0.25 parts per million of free chlorine residual. This ensures that the water is disinfected and remains free of any bacteria or other organics that might be harmful to the customer. Cayman Water tests approximately 65 samples of water each month for bacteria, in order to ensure that none is present in the water.

Any water will cause corrosion of metal. Cayman Water supplied desalinated water is relatively more aggressive than naturally occurring fresh water due to its low total alkalinity, its softness (lack of mineral content) and the residual salt present. Unlike many places in the world where hard water and scaling are problems, piped water in Grand Cayman is the opposite. It is very soft water thus more corrosive. Use plastic, brass or other corrosion resistant materials in your plumbing, especially for hot water heater fittings. Do not use galvanized steel fittings in your hot water plumbing to ensure prevention of leaks. Also, keep your hot water heater temperature as low in your comfort range as you can, which will mitigate corrosion and prolong the life of your water heater element.

All chemicals added to the drinking water stream in the production and treatment process are National Sanitary Foundation (NSF) approved for potable (drinking) water use. In addition to chlorine, Cayman Water adds a food grade sodium hydroxide (caustic soda) to adjust the pH of the water to just above 7, and it adds a zinc orthophosphate corrosion inhibitor to mitigate the corrosive effects of the water.

Environmental concerns include air pollution and greenhouse gas emissions from the power plants that provide electricity and/or thermal energy to the desalination plants.

Regardless of the method used, there is always a concentrated waste product consisting of everything that was removed from the created fresh water. This is sometimes referred to as brine, often disposed of in the ocean, and careful planning and design needs to ensure that this brine stream is dispersed as quickly as possible.

Marine life entrapment and impingement of the open sea intakes and brine outfalls for these systems is an environmental concern. Design improvements and extensive monitoring of existing systems have reduced the environmental impact of both.