Drinking water by itself does not promote defecation, it is important to understand the state of the stool in the intestine. From the time it is eaten in to the time it is excreted, there is a very important process of water reabsorption in the colon. The human body is a very economical precision instrument, it will keep the water in the body, especially when water shortage, it will absorb more, if not much shortage, not absorb. If the body is in a state of dehydration, the body is going to be more inclined to reabsorb water back into the feces, and the feces will become hard, and you will be constipated. So by drinking water and increasing the body’s hydration without dehydration, the chances of water being reabsorbed in the feces, is reduced a bit.