First of all, it might be normal to have a few tears escape from the eyes from time to time, especially if you have no other symptoms such as trouble seeing, or itching or redness of the eyes. However, to be sure you can get the eye checked out by your primary care doctor
or an eye doctor
By far one of the most common causes of excessive tear production would be eye allergies, or allergic conjunctivitis. This is an extremely common condition, especially during pollen seasons, but people can also be allergic to indoor allergies like mites and mold. The symptoms generally include tearing, and redness or itching of the eyes. The condition can be easily treated by medications from your doctor as well as by avoiding potential allergens.
Similarly, infections of the eye with either viruses or bacteria, as well as scratches or trauma to the surface of the eye can all cause excess tears. Again, these would be unlikely to be causes if you don't have other symptoms such as pain, redness, dryness, itching, etc.
Obstruction of a tear duct that drains from the eye into the nose is a very common cause of excessive tearing in children. It would be less common in adults, unless you were not diagnosed as a child or if you have another reason for an obstruction, such as a broken nose.
Talk to your primary care doctor, who will help you figure it out.