Pipe material usage: Which pipe type is commonly used for water or gas service and is also widely used as a soil pipe in building drainage systems?

Introduction / Context:
Different piping materials dominate particular services based on durability, corrosion resistance, and cost. Recognizing typical practice helps drafters and designers choose correct symbols and specifications on drawings.

Given Data / Assumptions:

• The material should be suitable for water or gas service.
• The same material should be commonly used as soil pipe.
• We are selecting among common building and municipal materials.

Concept / Approach:
Cast-iron pipe has a long history in water and gas distribution mains and is still widely used as soil pipe for gravity drainage and vent systems due to rigidity, fire resistance, and noise control. Soil pipe standards and fittings are well-established for cast-iron systems.

Step-by-Step Solution:

Verification / Alternative check:
Review plumbing code tables; cast-iron is listed for DWV systems (soil/waste/vent) and appears in historical municipal water/gas applications.

Why Other Options Are Wrong:

• PVC: Common for DWV and some water services, but not for gas service and not historically the soil pipe standard in heavy-duty applications.
• Copper: Potable water and HVAC; not used as soil pipe.
• Steel: Common for water/gas, but not common as soil pipe within buildings due to corrosion and noise concerns.

Common Pitfalls:
Assuming modern plastics have fully displaced cast-iron everywhere; many specs still favor cast-iron for DWV due to fire and acoustic performance.

Final Answer:
Cast-iron