What is the grade on a 6 inch pipe?

What is the grade on a 6 inch pipe?

• A. 1:80 or 1/10 in
• B. 1:50 or 1/2 in
• C. 1:100 or 1/8 in
• D. 1:200 or 1/20 in

Answer: (C)

The grade of a drainage pipe is the slope: how much vertical drop there is for a given horizontal run, usually expressed as a ratio or as inches of drop per foot. For gravity flow in a 6 inch drain, a common minimum slope is about 1/8 inch drop per foot. That corresponds to roughly a 1 vertical unit in about 100 horizontal units, i.e., about 1:100. So the option that lists 1:100 (which matches that 1/8 inch per foot approximation) is the best choice. The other options describe steeper or shallower slopes that don’t align with the typical minimum grade used for a 6 inch drain. For example, 1:50 or 1:80 would be too steep, while 1:200 would be too shallow for reliable gravity flow.

The grade of a drainage pipe is the slope: how much vertical drop there is for a given horizontal run, usually expressed as a ratio or as inches of drop per foot. For gravity flow in a 6 inch drain, a common minimum slope is about 1/8 inch drop per foot. That corresponds to roughly a 1 vertical unit in about 100 horizontal units, i.e., about 1:100.

So the option that lists 1:100 (which matches that 1/8 inch per foot approximation) is the best choice. The other options describe steeper or shallower slopes that don’t align with the typical minimum grade used for a 6 inch drain. For example, 1:50 or 1:80 would be too steep, while 1:200 would be too shallow for reliable gravity flow.