In a saucepan, add water,ginger,lemon juice,salt & mix well,bring it to boil & cook for 1-2 minutes.
Add rosemary,mix well and cook for 1-2 minutes then strain with the help of strainer.
Add maple syrup & mix well. Refrigerate until chilled.
Cut grapefruits into two halves and by using juicer machine squeeze the members to get as much as grapefruit juice as possible & set aside.
In a serving glass ,add ice cubes, grapefruit juice (1/4 cup),prepared rosemary maple syrup (3-4 tbs),7up and decorate with rosemary twig, grapefruit slice & serve!