Which of the following materials is NOT approved for water distribution piping under a slab?

In residential plumbing, especially for water distribution piping installed under a slab, certain materials are preferred or deemed acceptable based on their durability, resistivity to corrosion, and overall adaptability to different environmental conditions. While Copper Type M is commonly used for various plumbing applications, it is not recommended for applications under a concrete slab due to its thinner walls and lesser corrosion resistance compared to other copper types. Under conditions where it is more susceptible to damage or degradation, such as under concrete, it could lead to possible failures or leaks.

In contrast, Copper Type L and Type K pipes, with their thicker walls and higher durability, are typically approved for water distribution in applications where they may be exposed to soil and moisture, making them suitable for use under slabs. PVC piping, known for its corrosion resistance and lightweight properties, is also accepted for certain plumbing applications, though typically not under conditions that require pressurized water; it is mostly used for drainage, waste, and vent.

By understanding these material characteristics, it becomes evident why Copper Type M is the material not approved for use under a slab in water distribution systems, highlighting the importance of selecting the right pipe based on its intended application.