Dogs that drink a lot of water may be suffering from a medical condition called diabetes insipidus, or DII. This is when your dog's body is not producing enough of the hormone vasopressin, which controls how much water your body can excrete. To make up for this deficit, dogs naturally turn to their drinking behaviors -- they drink to get rid of excess fluid. This is especially true during times of stress, but also when dogs are in a state of dehydration. Because dogs can become very thirsty, owners should keep their pets on a regular schedule of drinking water. If a dog drinks too much water, there could be other health problems. Symptoms of DII include excessive drinking and urination.