Rule of thumb: 1 oz of water per pound of body weight per day
Dogs need approximately 1 ounce (30 mL) of water per pound of body weight per day. A 50-lb dog needs about 50 oz (~6 cups or 1.5 L). This increases with exercise, hot weather, dry food diets, lactation, and illness. Dogs on wet food diets get moisture from food and may drink less. Signs of dehydration: dry gums, skin tenting (slow return when pinched), sunken eyes, lethargy. Signs of excessive drinking (polydipsia, >100 mL/kg/day): may indicate diabetes, kidney disease, Cushing's disease, or liver disease — consult a vet. Always provide clean, fresh water. Some dogs prefer running water (fountains). During exercise, offer water every 15-20 minutes.