Distribute the grapefruit slices evenly throughout the mason jars, or add all to your pitcher.
Follow the same steps for the rosemary springs as you did with the grapefruit slices.
Stir all ingredients together. Put lids on your mason jars and put them in the fridge, or put your pitcher in the fridge to stay cool.
Your infused water should keep in the fridge for up to 2 days.