Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsEasy
A plumber is inspecting a newly installed 4-inch building sewer. What is the minimum required size for the cleanout fitting that serves this building sewer, according to most plumbing codes?
- A2 inches
- B3 inches
- C6 inches
- D4 inches
Show answer & explanationAnswer & explanation
Correct answer: D. 4 inches
Plumbing codes generally require cleanouts to be the same size as the pipe they serve, up to a certain maximum. For a 4-inch building sewer, the minimum required cleanout size is 4 inches to allow for proper access and cleaning. However, the maximum is often 4 inches, even for larger building sewers.
Why the other options are wrong
- A. 2 inches is too small for a 4-inch building sewer, inhibiting effective cleaning.
- B. 3 inches is also too small for a 4-inch building sewer.
- C. 6 inches would be unnecessarily large and is not typically required for a 4-inch pipe, though it might be used for larger sewers.
Building Sewer Cleanout Size
The minimum diameter of a cleanout fitting required for a building sewer, generally matching the diameter of the sewer pipe it serves.
- Provides access for clearing blockages.
- Must be accessible for rodding tools.
- Typically the same size as the drain pipe, up to 4 inches.
- Larger sewers (e.g., 6-inch) often still use 4-inch cleanouts.
Memory trick: Cleanout Size: Match the Pipe, Keep it Tight.