During a visit to Bermuda some 20 years ago I recall being told that all houses (new construction?) had concrete water tanks in their basement which stored the rainwater collected by the also mandated terraced concrete roofs. The roofs were hurricane resistant as well; and the material in both "sweetened" any acid in the rain. The idea was make each home more or less water self-sufficient. Others who have been or live there might comment, or supply links to pictures/designs