'05 Xterra S...leak in windshield washer reservoir

I'm pretty sure there is a leak or hole somewhere in the system. My warning light came up and I filled it up with a 1/2 gallon of fluid and the light went off. One or two days later, the light went on again and so I filled it up again. The second time I did it in my garage and there is a puddle of windshield washer fluid on the floor near the front passenger side tire. Any ideas on how to locate or fix this problem. It's kind of a weird one because I don't know how I possibly could have developed a leak.