A 2 in. horizontal sanitary branch is laid out in a ceiling space. Which minimum slope is commonly required for small horizontal drainage piping?
Correct Answer
D) 1/4 in. per ft
Small horizontal drainage piping, such as 2 in. pipe, is commonly sloped at 1/4 in. per ft. Other choices are too flat for small sanitary branches or steeper than the usual minimum.
Why This Is the Correct Answer
Small horizontal drainage piping, such as 2 in. pipe, is commonly sloped at 1/4 in. per ft. Other choices are too flat for small sanitary branches or steeper than the usual minimum.
Why the Other Options Are Wrong
Option A: 1/8 in. per ft
Choice A (1/8 in. per ft) is rejected because 1/8 in. per ft is a different drainage slope than the pipe size in the item; the accepted slope is 1/4 in. per ft. The cited answer is 1/4 in. per ft.
Option B: 1 in. per ft
In mechanical and plumbing, 1 in. per ft is the wrong selection for Drainage slope: 1 in. per ft is a different drainage slope than the pipe size in the item; the accepted slope is 1/4 in. per ft.
Option C: 1/2 in. per ft
The trap in C is 1/2 in. per ft. That selection is wrong because 1/2 in. per ft is a different drainage slope than the pipe size in the item; the accepted slope is 1/4 in. per ft; Small horizontal drainage piping is commonly sloped at 1/4 in. per ft.
Memory Technique
Treat drainage slope like a labeled shelf; only the matching condition belongs with 1/4 in. per ft.
Reference Hint
Open Pipe and Excavation Contracting, 2011; use the index entry or section for "Gravity drainage pipe slope for small sanitary branches" to confirm that Small horizontal drainage piping, such as 2 in.
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