Master Plumber Practice Exam

What is the maximum allowable slope for a horizontal drainage pipe?

1. 1/4 inch per foot

2. 1/8 inch per foot

3. 1/2 inch per foot

4. 3/4 inch per foot

The correct answer is: 1/4 inch per foot

The maximum allowable slope for a horizontal drainage pipe is 1/4 inch per foot. This standard is in place to ensure optimal drainage and prevent issues such as clogging or inadequate flow. A slope that is too steep could cause wastewater to move too quickly through the pipe, leading to a lack of proper scouring of the pipe walls and potentially allowing solids to settle. Conversely, a slope that is too shallow may not provide sufficient gravitational pull for effective drainage, also resulting in blockages. This standard reflects the balance required to maintain effective waste transport while minimizing the risk of plumbing issues. The other options suggest slopes that either exceed this recommendation or fall below what is considered effective for drainage systems, which could lead to inefficient waste removal. This 1/4 inch per foot specification is widely accepted in plumbing codes and best practices for effective drainage management.