What type of pipe is most appropriate for underground service lines?

HDPE (High-Density Polyethylene) is the most appropriate type of pipe for underground service lines due to its excellent resistance to corrosion, chemical exposure, and environmental stress. It also offers significant flexibility, allowing it to adapt to ground movement without cracking. This feature makes it particularly suitable for various soil conditions and environments where settling or shifting can occur.

Additionally, HDPE can be fused together to create a joint-free system, which minimizes the risk of leaks and enhances the overall durability of the installation. The pipe's light weight and ease of installation further contribute to its effectiveness for underground applications, making it a preferred choice for utility lines, including water and gas distribution.

In contrast, other materials such as PVC are commonly used above ground and in certain underground applications but do not match the flexibility and resilience of HDPE in challenging soil conditions. CPVC, while effective in hot water applications, is also not ideal for underground service due to its brittleness. ABS is generally used for drainage, waste, and vent systems, and is not recommended for pressurized service lines underground.