Water distribution networks are a significant investment. As such, a large volume of research has examined the pipe design/rehabilitation problem and is summarized in other papers. This paper focuses on the application of a new optimization method to the pipe sizing problem. In recent years, the researchers have attempted to exploit expanding computer power and combined new optimization techniques with hydraulic simulation software. The computer model in this work, SFLANET, is based upon the shuffled frog leaping algorithm (SFLA), a memetic algorithm (a kind of meta-heuristic). The optimization algorithm is linked to EPANET via the EPANET Toolkit and can be used to design large, complex pipe network systems. Here results are shown for the New York City Tunnel problem. Copyright ASCE 2004.