Any water will cause corrosion of metal. 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 (i.e. it has fewer dissolved minerals) and as a result is more likely to draw minerals from pipes. Use plastic, brass or other corrosion resistant materials in your plumbing, especially hot water heater fittings. Replace galvanized steel fittings in your hot water plumbing to prevent leaks. Also, keeping your hot water heater temperature as low in your comfort range as you can will mitigate corrosion and prolong your water heater element life.