Which types of plastic pipe shall not be used to supply fuel gas?

Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) are not suitable for supplying fuel gas due to their chemical properties and the potential for degradation when exposed to certain fuels and the high temperatures that can be encountered in gas applications.

PVC and CPVC pipes are commonly used for water supply and drainage systems because they are resistant to corrosion and chemicals. However, these materials can become brittle when subjected to the pressures and chemical exposure associated with fuel gases. Additionally, they can release harmful substances when exposed to heat or combustion, making them unsafe for transporting fuel gases.

In this context, other types of plastic pipes, like high-density polyethylene (HDPE) and polypropylene (PP), are sometimes accepted for fuel gas applications, and materials like PEX can be used in certain situations, depending on local codes and regulations. Fiberglass, while not a traditional gas transport material, is sometimes employed in specific industrial applications but should be carefully evaluated against safety standards when handling gas.

Thus, the correct choice highlights the specific limitations of PVC and CPVC in the context of fuel gas supply, making them unsuitable for this purpose.