What is the minimum size of a cleanout serving a 4-inch drain line?

What is the minimum size of a cleanout serving a 4-inch drain line?

• A. 2 inches
• B. 3 inches
• C. 4 inches
• D. 6 inches

Answer: (C)

The key idea is that a cleanout must be sized to allow proper access for cleaning tools. For a drain line with a 4-inch diameter, the cleanout must be at least the same size as the pipe so a rod or snake can pass through and effectively clear blockages. If the cleanout were smaller, access would be restricted and cleaning would be impractical or noncompliant with typical plumbing codes. A larger cleanout isn’t required for this minimum; the 4-inch size meets the requirement without being excessive. So, the smallest cleanout that serves a 4-inch drain line is 4 inches.

The key idea is that a cleanout must be sized to allow proper access for cleaning tools. For a drain line with a 4-inch diameter, the cleanout must be at least the same size as the pipe so a rod or snake can pass through and effectively clear blockages. If the cleanout were smaller, access would be restricted and cleaning would be impractical or noncompliant with typical plumbing codes. A larger cleanout isn’t required for this minimum; the 4-inch size meets the requirement without being excessive. So, the smallest cleanout that serves a 4-inch drain line is 4 inches.