National Home Inspector Practice Exam

What is the proper slope for a drain line?

1. 1/4 inch to 1/2 inch per foot

2. Less than 1/4 inch per foot

3. 1 inch per foot

4. No slope

The correct answer is: 1/4 inch to 1/2 inch per foot

The proper slope for a drain line is indeed important for ensuring effective drainage. A slope of 1/4 inch to 1/2 inch per foot is recommended because it allows wastewater to flow adequately towards the drainage system without causing backups. This range provides enough angle to encourage gravity-driven flow while preventing the accumulation of solids, which could lead to clogs. The rationale behind this specific range is rooted in plumbing principles that dictate how fluids behave in pipelines. If the slope is too shallow (less than 1/4 inch per foot), there is a risk that water will not flow efficiently, possibly leading to stagnant water or blockages over time. On the other hand, too steep of a slope, such as 1 inch per foot, can result in water flowing too quickly, which can allow solids to settle rather than being carried away. A drain line with no slope would not be functional, leading to serious drainage issues. Using the recommended slope ensures that wastewater is effectively moved away from the home and that the plumbing system operates as intended.