Thanks for your question. First of all, we have to understand that our body consists of 70% water. Water is removing waste materials from our body. It also helps for moving the other nutrients around the body.It keeps our body temperature correct. If we lose water from the body like sweating our body remains cool. Generally, a person should drink 3 or 4 liters of water per day. But in the gym, you should drink 8 liters water per day. Because in the gym, you burn a lot of calories. Many body builders drink 10 liters of water per day when they take supplements .After all, water is an important ingredient in bodybuilding. So you should drink a lot of water. I think you find the answer to your question.