Bring 4 cups of water to boil in a medium saucepan. Once boiling, remove from the heat, and add the hibiscus flowers. Let steep for 15 minutes.
Strain the flowers out of the tea, pressing into the flowers to extract any remaining water. Pour the strained tea into a large pitcher. Discard the flowers.
Add the remaining 4 cups of water, juice from 1 lime, and ½ cup of sugar. Stir well to combine. Adjust the sugar or lime to to taste.
Store in the refrigerator until cooled, then serve over ice.