Drinking water can help you lose weight, whether you're restricting your calories or not. Consuming 2 cups of water before a meal helped a group of obese adults lose 2 pounds over a 12-week period without making any other changes to their usual intake, according to a 2015 clinical study published in Obesity.
How many tea bags should you use to make a half gallon of iced tea? One gallon is about 128 ounces, so if one tea bag is good for 10 oz  of water, then about 10 teabags is good for a gallon. Start with 10  and adjust accordingly with water.
This is so that you don't have to boil a whole gallon of water. You could even boil 2 cups of water and make a sort of tea concentrate with 16 tea bags, but just add water to make a gallon and there ya go. Cool or chill to make iced tea. Good luck.