Which of the following materials is NOT commonly used in piping systems?

Aluminum is not commonly used in piping systems for a variety of reasons, making it the correct choice in this question. While aluminum is a lightweight metal with good corrosion resistance and is often found in construction and manufacturing applications, it is relatively less used in traditional piping systems compared to the other materials listed.

Steel is widely used due to its strength and durability, making it suitable for high-pressure applications. Copper is preferred for its excellent thermal conductivity and resistance to corrosion, especially in plumbing and refrigeration systems. PVC is commonly used for its low cost, ease of installation, and resistance to chemicals, making it popular for drainage, waste, and vent systems.

In contrast, the use of aluminum in piping is limited primarily because it can be susceptible to galvanic corrosion when in contact with other metals, requires special handling when welded, and does not have as high a strength-to-weight ratio in demanding applications as steel. As a result, while aluminum has its advantages, it is not a material that is regularly employed in standard piping systems.