Massachusetts Plumbers Journeyman Practice Exam

For building drains inside a building, what type of drain piping shall be used if it encompasses the water service pipe within the trench?

1. Cast iron tarred soil pipe

2. PVC pipe

3. Steel pipe

4. Copper pipe

The correct answer is: Cast iron tarred soil pipe

Using cast iron tarred soil pipe for building drains that encompass the water service pipe within the trench is appropriate because cast iron offers excellent durability and resistance to external pressures. This type of pipe is specifically designed for underground applications where soil conditions and potential impacts on the piping can be a concern. The tarred coating further enhances its resistance to moisture and corrosive elements in the soil, which is critical when dealing with drains that may face various environmental factors. In contrast, other materials like PVC, while lightweight and resistant to corrosion, may not provide the same strength and durability when systems are subjected to significant external loads. Steel pipe, although robust, can be susceptible to rusting and corrosion over time unless properly treated or coated. Copper pipe, while great for certain applications, is generally not used for drainage due to cost and potential reactions with soil chemicals. Choosing cast iron tarred soil pipe ensures compliance with building codes and best practices for plumbing infrastructure, particularly where water service lines might be in close proximity. This helps to maintain the integrity of the system and avoids potential hazards associated with other pipe materials.