In a large pot bring the water to a boil. Remove pot from heat, add the tea bags, cover with a lid, and allow tea to steep in water for 20 minutes. Take a 1 gallon jug and pour the sugar into the jug and cover with some hot tap water. Stir the sugar around to dissolve while the tea is steeping. Once the tea has steeped, remove the lid and the tea bags. Pour the tea into the jug with the sugar, stir, and place the tea bags back into the jug. Stir the tea well, making sure the sugar dissolves. Fill the jug with cold water to yield 1 gallon.
To serve, pour each glass of tea and garnish with a slice of lemon and mint leaves.