WebMD reports that the main reasons that dogs drink an excessive amount of water are dehydration, illness, medication and diet. Most dogs needs 1 ounce of fluid per pound of body weight on a daily basis. On average, a 10-pound dog requires just a little over 1 cup of water each day. Very active dogs, lactating mothers and young puppies may generally drink more water.
WebMD outlines the factors that can contribute to dehydration, which include heat, high activity levels during play, illness and infection. Physical signs of dehydration include lethargy, thick rope-like saliva, and dry gums and tongue. Dehydration can be life-threatening, so seek veterinary attention if you suspect serious dehydration. If your dog is not vomiting and you suspect dehydration, give your dog small amounts of water (a teaspoon for little dogs and 1-2 tablespoons for larger dogs) with a spoon every 10 minutes for a few hours.
According to WebMD, illnesses that can cause excessive drinking include liver disease, diabetes, Cushing's disease, cancer, diarrhea, fever, infection and kidney disease. Drugs that make a dog thirsty are anti-inflammatory drugs, heart failure drugs and seizure medications. A dry food diet or high sodium diet can also lead to excessive thirst in your dog.