Dogs need to stay hydrated, so a dog refusing to drink water is a cause for concern. You should expect the animal to drink water willingly and enthusiastically, several times a day. If he does not drink water at all for a day or two, he bows his head to one side when offered water, then he probably has problems: old age, dirty water, dehydration, urinary tract infections, diseases and mouth lesions. Water is essential for animal health. Dogs that do not drink water for more than a day may become dehydrated, which can be life-threatening and may need medical attention.