Dr. Mohammad Najafi, P.E., F. ASCE, Director of the Center for Underground Infrastructure Research and Education (CUIRE) received a competitive research grant from Water Research Foundation (WRF) for the U.S. Environmental Protection Agency's program on "Innovation and Research for Water Infrastructure for the 21st Century." The cities of Seattle (Washington), Dallas (Texas), Fort Worth (Texas), Miami Dade County (Florida), Arlington (Texas), Rowlett (Texas), Charlotte (North Carolina) and the Tarrant Regional Water District (TRWD, Fort Worth, Texas) in addition to Black & Veatch Corporation (Kansas City, Missouri) and Benton and Associates (Jacksonville, Illinois) provide technical assistance and $114,000 financial support for this project, making the total project budget $264,000. Drinking water infrastructure in the North America is in dire need of renewal and large diameter transmission mains are perhaps the most critical element of a water distribution system, since a failure can be catastrophic in addition to extended service interruptions for many customers and water quality concerns. Where rehabilitation by relining of an old and deteriorated large diameter water main is not feasible due to capacity concerns and structural integrity, replacement is inevitable. Recent advancements in polymer science resulted in production of high-strength and durable, large diameter (24-inch and larger) high density polyethylene (HDPE) pipes with thick walls (up to 4 inches). HDPE can be a cost effective alternative, and perhaps the most reliable in terms of preserving water and water quality in transmission and distribution systems. However, most engineers and water purveyors are reluctant to use HDPE due to lack of experience with its durability and reliability. Therefore, the objective of this study is to determine the durability and reliability of large diameter (from 24 to 48 inches internal diameter) HDPE water mains as an economical alternative to other pipe materials.