What is the clean out size on a branch serving six lavatories?

What is the clean out size on a branch serving six lavatories?

• A. 1/2 inch
• B. 1 inch
• C. 2 inch
• D. 3 inch

Answer: (C)

The main idea is that a cleanout should be sized to the drain it accesses. When a branch serves multiple fixtures, the branch itself is sized to handle the combined flow, and the cleanout is then made the same size as that branch so you have proper access for clearing blockages. For a branch feeding six lavatories, the common practice is to use a 2-inch drain branch. A 2-inch cleanout allows adequate access and capacity for clearing the line, whereas a smaller size would limit access and capacity, and a much larger size is not typically required for a bathroom group. So the correct cleanout size is two inches.

The main idea is that a cleanout should be sized to the drain it accesses. When a branch serves multiple fixtures, the branch itself is sized to handle the combined flow, and the cleanout is then made the same size as that branch so you have proper access for clearing blockages. For a branch feeding six lavatories, the common practice is to use a 2-inch drain branch. A 2-inch cleanout allows adequate access and capacity for clearing the line, whereas a smaller size would limit access and capacity, and a much larger size is not typically required for a bathroom group. So the correct cleanout size is two inches.