How much does a racehorse pee? A lot. Horses typically produce several quarts of urine every four hours, for a total of about 1.5 to 2 gallons per day. (By contrast, an adult male human pees 1 or 2 quarts per day.) The stream, usually one-third to a half-inch in diameter, can last up to 30 seconds. In general, the larger the animal, the more it pees.