1. (a) The only acceptable materials for the underground portion of a closed-loop geothermal system are as follows:

   1. (1) Copper, that has a cathodic protection system;
   2. (2) High density, polyethylene extrusion compound having a cell classification of PE 345434c or PE 355434c with an ultraviolet stabilizer of C, D or E as specified in American Society for Testing and Materials (“ASTM”) standard D-3350 with the following exception: This material shall exhibit zero (0) failures when tested for one hundred ninety-two (192) hours or more under ASTM standard D-1693, condition C, as required in ASTM standard D-3350. This material shall maintain a one hundred sixty (160) pounds per square inch (“psi”) hydrostatic design basis at 73.4 degrees Fahrenheit per ASTM standard D-2837, and shall be listed in PPI TR4 as a PE 3408 piping formulation; and (3) Those materials approved by the department in consultation with the Department of Public Health and the Department of Energy and Environmental Protection.

2. (b) The only acceptable methods for joining sections of buried geothermal piping are as follows:

   1. (1) For copper piping assemblies, by the use of brazed joints;
   2. (2) For polyethylene piping assemblies, by use of the heat fusion process in accordance with the pipe manufacturer's specifications, or by use of mechanical stab fittings approved by the International Ground Source Heat Pump Association (“IGSHPA”); and (3) For piping made of materials approved pursuant to subsection (a)(3) of this section, by the use of those methods approved by the department in consultation with the Department of Public Health and the Department of Energy and Environmental Protection.
3. (c) All geothermal systems shall be pressure tested with water, air, or an inert gas to a minimum of one hundred fifty (150) per cent above the heat pump manufacturer’s operating specifications for a minimum period of thirty (30) minutes before being put into service. Any system found to leak shall be repaired or replaced and then retested before being put into service.

(Effective July 8, 2022)