CSLB C-36 Plumbing ContractorPlanning and EstimatingEasy
A plumbing contractor is planning to install a new drainage system for a 2-story commercial building. The plans specify 4-inch PVC Schedule 40 pipe for the main building drain. What is the primary reason for selecting Schedule 40 PVC over Schedule 20 PVC for this application?
- ASchedule 40 PVC has a smoother interior surface for better flow.
- BSchedule 20 PVC is not approved for commercial drainage systems.
- CSchedule 20 PVC is more expensive than Schedule 40 PVC.
- DSchedule 40 PVC offers greater wall thickness and pressure resistance.
Show answer & explanationAnswer & explanation
Correct answer: D. Schedule 40 PVC offers greater wall thickness and pressure resistance.
Schedule 40 PVC pipe has a thicker wall compared to Schedule 20 PVC (which is often referred to as 'thin-wall' pipe). This increased wall thickness provides greater strength and pressure resistance, making it suitable for main building drains where durability and structural integrity are critical.
Why the other options are wrong
- A. While surface smoothness can impact flow, the primary distinction between Schedule 20 and 40 is wall thickness, not surface finish.
- B. Schedule 20 PVC can be approved for certain non-pressure drainage applications, but not typically for main building drains due to lower strength.
- C. Schedule 20 PVC is generally less expensive than Schedule 40 PVC due to less material used in its construction.
PVC Schedule 40 vs. Schedule 20
PVC pipe schedules (e.g., 40, 20) denote wall thickness, with higher numbers indicating thicker walls and greater strength.
- Schedule 40 is standard for pressure and drainage applications requiring higher strength.
- Schedule 20 (thin-wall) is used for non-pressure, non-critical drainage or vent applications.
- Wall thickness directly impacts pipe's pressure rating and durability.
Memory trick: Thicker walls mean tougher pipes, just like a strong fort.