To make a simple syrup, combine sugar, salt, and ½ cup water in a small pot. Bring to a boil. Stir, and reduce heat to medium high. Stir occasionally until sugar is dissolved, approximately 5 minutes. Let the simple syrup cool.
Add 4 cups of water, lime juice, and 6 Tbsp of the simple syrup to a pitcher. Stir well, and chill.