CSLB C-36 Plumbing ContractorRough-in PlumbingHard
A plumbing contractor is installing a new residential DWV system. A 3-inch horizontal drain pipe transitions to a 3-inch vertical stack. What is the maximum permissible angle for a fitting connecting a horizontal drain to a vertical stack to be considered a 'stack fitting' for DWV purposes?
- A60 degrees (1/6 bend)
- B22.5 degrees (1/16 bend)
- C45 degrees (1/8 bend)
- D90 degrees (1/4 bend)
Show answer & explanationAnswer & explanation
Correct answer: C. 45 degrees (1/8 bend)
The California Plumbing Code (CPC) specifies that horizontal drainage pipes connecting to vertical stacks must do so with fittings that allow for a smooth transition to prevent flow impedance and turbulence. A 45-degree (1/8 bend) fitting is the maximum permissible angle for a horizontal drain to enter a vertical stack without requiring additional consideration for flow dynamics, although smoother transitions with lesser angles are also permitted.
Why the other options are wrong
- A. A 60-degree bend is too abrupt and would likely cause turbulence and impede drainage when connecting a horizontal drain to a vertical stack.
- B. A 22.5-degree bend would provide a very smooth transition but is not the maximum allowed.
- D. A 90-degree bend (tee or short sweep elbow) is generally not permitted for horizontal to vertical drainage connections due to severe flow restriction and potential for clogging.
Horizontal to Vertical Drain Connection
The method and maximum angle of fittings used to connect a horizontal drainage pipe to a vertical drainage stack, critical for maintaining proper flow and preventing blockages.
- Ensures smooth wastewater flow.
- Prevents turbulence and blockages.
- Specific fitting types and angles are code-mandated.
Memory trick: Horizontal to Vertical: 'Forty-Five' is the 'Fair' angle for Flow.