Question: why do a dogs eyes water?
Answer: Conjunctivitis. Mucus, yellow-green pus, or a watery eye discharge can all be signs of conjunctivitis, an inflammation of the lining of your dog's eye. There's a wide range of causes for conjunctivitis, from allergies, injury, birth defects, and tear duct problems, to foreign matter, dry eye, distemper, or even tumors.