What is the maximum length of a 3-inch trap arm installed with a slope of 1/4 inch per foot (1:50)?

What is the maximum length of a 3-inch trap arm installed with a slope of 1/4 inch per foot (1:50)?

• A. 3.75m or 12'
• B. 2.5m or 8'
• C. 4.0m or 13'
• D. 6.0m or 20'

Answer: (A)

The key idea is that trap arm length is limited by the trap size and the slope to maintain proper drainage and venting. With a fixed slope of 1/4 inch per foot, plumbing codes provide a table that specifies the maximum trap arm length for each trap diameter. For a 3-inch trap, the allowable length is 12 feet. That corresponds to about 3.75 meters. So the maximum length is 12 feet (3.75 m), which is the correct choice. The other lengths would apply to smaller trap sizes or different slopes, not a 3-inch trap with this slope.

The key idea is that trap arm length is limited by the trap size and the slope to maintain proper drainage and venting. With a fixed slope of 1/4 inch per foot, plumbing codes provide a table that specifies the maximum trap arm length for each trap diameter. For a 3-inch trap, the allowable length is 12 feet. That corresponds to about 3.75 meters. So the maximum length is 12 feet (3.75 m), which is the correct choice. The other lengths would apply to smaller trap sizes or different slopes, not a 3-inch trap with this slope.