Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsEasy
A plumber is inspecting a newly installed 4-inch building sewer. What is the minimum required cleanout size for this pipe?
- A3 inches
- B4 inches
- C2 inches
- D5 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 4 inches
According to plumbing codes, cleanouts must generally be the same size as the pipe they serve, up to a certain maximum. For a 4-inch building sewer, the minimum cleanout size is 4 inches.
Why the other options are wrong
- A. This is too small; cleanouts should generally be the same size as the pipe they serve.
- C. This is too small; cleanouts should generally be the same size as the pipe they serve.
- D. While larger is often acceptable, 5 inches is not the minimum required size for a 4-inch pipe.
Cleanout Sizing
Cleanouts are access points in a DWV system that allow for the clearing of blockages. Their size is typically dictated by the diameter of the drainage pipe they serve.
- Cleanout size generally matches pipe size.
- Minimum 1 1/2 inches for 1 1/2" to 2" pipes.
- Minimum 2 inches for 2 1/2" to 3" pipes.
- Minimum 3 inches for 4" pipes and larger (or same size as pipe up to 4").
Memory trick: Cleanouts Match Pipe Diameter for Clear Passage.