Dogs have a normal water intake of about 10 to 20 millilitres per kilogram of body weight per day, or about 3 to 4 glasses of water per day for a dog weighing around 10 kilograms. Anything more than that, under normal environmental conditions, is considered polydipsia.
Polydipsia (excessive thirst) is not normal for a dog. It is usually a symptom of some underlying problem that can be caused by Diabetes, Cushing’s disease, Liver Disease etc.
If you feel your dog is drinking too much water, do not deprive him of this because if there is something wrong, then the chances of it becoming worse are greater if your dog has less water.
Instead, take your dog to your local Vet who will probably run a few tests (blood test and a urine analysis) and he/she will decide on the best treatment for your dog depending on the results.