Clinical studies conducted at the Johns Hopkins School of Medicine showed that the Chiroflow Water Pillow helps reduced the intensity or level of morning pain, increases pain relief and most importantly, improves the quality of sleep. It features a pouch which you fill with water, the amount of which will determine your level of comfort and support. The water inside the pouch can be left inside the pillow for a maximum of one year. You can change the water on the pouch at the same time that you wash your pillow. It is advisable that you use tap water because the chlorine content is enough to prevent bacteria growth.