PEX-A tubing is cross-linked, high-density polyethylene. All Apollo? Expansion PEX is opaque in color and ensures easy identification of hot, cold and main water lines through different colored print lines. Apollo? Expansion PEX pipe is produced using the high-pressure peroxide method for crosslinked polyethylene (PEXa) in accordance with ASTM F876, F877, CSA B137.5 and PPI TR-3 and is certified to NSF 14/61 standards. Apollo? Expansion PEX pipe also meets the requirements of ASTM F2023 for chlorine resistance. Apollo? Expansion PEX pipe is manufactured using a quality management system which has been certified to the latest version of ISO 9001. Use of Apollo? Expansion PEX pipe in heating systems requires corrosion protection and/or isolation by using a heat exchanger or non-ferrous components throughout the system.