Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsEasy
A plumber is designing a DWV system where a portion of the horizontal drainage piping will be installed underground outside the building. Which of the following materials is generally NOT approved for underground building sewer installations?
- AABS (Acrylonitrile Butadiene Styrene) schedule 40
- BPVC (Polyvinyl Chloride) schedule 40
- CGalvanized steel
- DService weight cast iron
Show answer & explanationAnswer & explanation
Correct answer: C. Galvanized steel
Galvanized steel pipe is rarely approved for underground drainage or sewer applications due to its susceptibility to external corrosion and the eventual degradation of the zinc coating, leading to pipe failure.
Why the other options are wrong
- A. ABS Schedule 40 is also a commonly approved and used material for underground building sewers, similar to PVC.
- B. PVC Schedule 40 is widely accepted for underground building sewers due to its corrosion resistance and ease of installation.
- D. Service weight cast iron is commonly approved and used for underground building sewers due to its strength and durability.
Underground DWV Material Suitability
The appropriateness of various piping materials for burial in soil to convey drainage, waste, and vent, considering factors like corrosion, strength, and longevity.
- Corrosion resistance is paramount for underground pipes.
- Strength to withstand earth loads is important.
- Material must be approved by local plumbing codes.
Memory trick: Buried Pipes Pick Proper Plastics.