Callaway Nuclear Plant is the first nuclear plant in the United States to utilize high density polyethylene (HDPE) piping in a nuclear safety-related application. HDPE is being installed in buried sections of the plant’s ASME Section III, Class 3 Essential Service Water (ESW) system. Due to its resistance to erosion, corrosion and microbiologically induced corrosion (MIC), HDPE is well suited to raw water system applications. As with any other first of a kind project, the use of HDPE piping in the Callaway ESW system has presented challenges in all phases of the project. Design, qualification and installation considerations for thermally-fused HDPE in an ASME Class 3 system differ significantly from those for traditional metallic materials. This paper will examine the challenges and lessons learned in the design, qualification testing, installation, examination and pressure testing of the HDPE piping at Callaway Nuclear Plant.