Ground heat exchanger piping materials must provide corrosion resistance, chemical resistance, temperature resistance, flexibility, impact resistance, resistance to slow crack growth, and long-term hydrostatic strength (pressure capability). In addition, ground loop heat exchanger materials must provide suitable heat transfer capabilities, since conducting heat with the earth is the primary function of the ground loop. To help ensure that only the most reliable and capable piping materials are used for these demanding applications, the Piping sections of the new CSA/ANSI/IGSHPA C448 Series 25 have been significantly updated. Section 5.4 “Underground and Underwater Piping” includes new materials allowed for ground heat exchangers and increased compliance requirements for piping. A revised Section 5.6 “Interior Piping” also includes new materials and requirements. For the first time, C448 includes a new Section 8.4 “Installation of Ground Heat Exchanger Piping” as well as new Section 9.2 “Hydrostatic Pressure Tests”. This presentation will explain the new requirements in C448:25 by describing the materials that comply with these requirements, and will also introduce new sections for installation and testing.