Arizona Plumbing Practice Exam

Which of the following materials is not approved for use in an interior water distribution system?

1. PVC pipe (ASTM D1789)

2. Copper pipe

3. PEX tubing

4. Galvanized steel

The correct answer is: PVC pipe (ASTM D1789)

In interior water distribution systems, certain materials are specified based on their performance, safety, and long-term durability when used for transporting potable water. PVC pipe, specifically the type referenced by ASTM D1789, is generally not approved for use in hot or cold water distribution systems. This is due to concerns regarding its ability to handle high temperatures and pressures, as well as potential leaching of harmful substances into the water supply. Additionally, PVC can become brittle over time, especially when exposed to ultraviolet light if it is not properly shielded. In contrast, copper pipe is widely accepted and has been a standard choice for plumbing due to its excellent durability, resistance to corrosion, and ability to withstand high temperatures. PEX tubing is also approved and increasingly popular for its flexibility, ease of installation, and resistance to scale and chlorine, as well as reduced freezing risk. Galvanized steel, although less common now, has been used and can be approved in certain applications due to its strength and ability to resist fire. Therefore, the material that is not approved for use in an interior water distribution system is PVC pipe as described.