A contractor is reviewing a plumbing plan that shows a 4-inch sanitary sewer line running 150 feet with a minimum slope of 1%. What is the total vertical drop of this pipe?
Correct Answer
D) 18 inches
A 1% slope means 1 foot of drop per 100 feet of horizontal run. For 150 feet: 150 × 0.01 = 1.5 feet = 18 inches of total drop.
Why This Is the Correct Answer
A 1% slope means 1 foot of vertical drop for every 100 feet of horizontal distance. When applied to 150 feet of pipe run, this equals 1.5 feet of total drop. Converting 1.5 feet to inches (1.5 × 12 = 18 inches) gives us the answer in the units requested. Option B correctly identifies this as 18 inches.
Why the Other Options Are Wrong
Option A: 0.15 feet
This represents 0.15 feet, which would be the drop for only 15 feet of pipe run (15 × 0.01 = 0.15), not 150 feet. This appears to be a decimal place error in the calculation.
Option C: 1.5 feet
This represents 15 inches, which equals 1.25 feet. This would be the correct drop for 125 feet of pipe (125 × 0.01 = 1.25 feet), not 150 feet as specified in the problem.
Memory Technique
Remember '1% = 1 foot per 100 feet' - then just multiply: 150 feet ÷ 100 feet = 1.5, so 1.5 × 1 foot = 1.5 feet drop
Reference Hint
Florida Building Code - Plumbing, Chapter 7 (Sanitary Drainage) or IPC Chapter 7 for minimum slope requirements for drainage piping
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