From Wikipedia (the Internet encyclopedia) article Fluid ounce : A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl.) is a unit of volume typically used for measuring liquids. A US fluid ounce is 1⁄128 of a US liquid gallon. So, 1 oz =of a gallon. Hence, 15 oz = of a gallon. 15 oz per minute = of a gallon per minute = gallons per hour = gal/h = gal/h = gal/h = 7.03125 gal/h. ANSWER. The flow rate of 15 oz/min is the same as the flow rate of gal/h = gal/h = 7.03125 gal/h.