Water accounts for about 25% of the weight of a single hair strand. Ensuring that you drink enough water energizes and supports hair growth all the way from the scalp to the ends of the hair strand. Dehydration can cause hair to stop growing. Your hair roots, are the only pipeline that water is supplied from the body to your hair so to put it simply; if you want your postpartum hair to grow back; you need to be drinking enough water. But how much is actually enough?