Increased water intake can be a sign of many different diseases, including, but not limited to; kidney failure, Cushing's disease, Diabetes, Hyperthyroidism, kidney disease or urinary tract infection, and Pyometra (infection of the uterus) to name a few. It can also be seen when taking some medications, such as Prednisone.
How Much Water Should My Pet Drink? Diet and environment will cause some differences in water requirements, but an average daily intake for dogs and cats should be about 30ml per pound per 24 hours.* For reference, 30ml is approximately 1 fluid ounce.
Note: Some of the daily fluid intake will be found in food too, especially with a moist diet, such as canned or raw versus kibble.
Puppies and kittens have a higher fluid requirement. If you notice a change in your pet's fluid intake (and subsequent increased urine output or increased urinary accidents) call your veterinarian for an examination.
One exception for urinary accidents would be a senior pet with cognitive dysfunction or dementia (disoriented, forgetting housetraining), but other more common medical conditions must be ruled out first.
* Textbook of Veterinary Internal Medicine, Vol 1, EttingerPhoto credit: Two dogs drinking water © Steven Fernandez on Flickr