I spoke about the need to moisturize hair in this post. Apart from applying it topically, there is also a need to drink enough water so that the body has enough of a supply to carry out its functions efficiently.
Your skin, hair and entire system benefit from being fed water. Your hair is moisturized from within, your skin is supple and your body is able to eliminate waste more efficiently leading to less toxins residing in the body.
I found this handy illustration of just how much water you need to drink per day at a minimum for your body weight. I hope you find it helpful. More information here. An easy way of achieving your daily quota is using a water bottle or refilling a 1.5 litre bottle and ensuring that you finish it every day. Following the guidelines on the site, you may need more.
Always drink water a few minutes after you wake up. According to this book, it helps immensely in the evacuation process. As far as I know, there are no benefits in housing toxins in the body so flush them out with water!