What is the drainage piping slope for pipes that are 3 inches and above in diameter?

The correct drainage piping slope for pipes that are 3 inches and above in diameter is 1/4 inch per foot. This slope is crucial for ensuring that wastewater flows effectively through the pipes, minimizing the potential for blockages and allowing for proper drainage.

In plumbing systems, especially for larger diameter pipes, a steeper slope is required to maintain flow velocity and to compensate for the volume of waste and water being transported. A slope of 1/4 inch per foot is the standard used in most plumbing codes and practices, as it is generally seen as the minimum effective slope for efficient drainage.

The other options, which suggest lesser slopes, do not provide adequate drainage for pipes of this size. A slope of 1/8 inch or lower would lead to inadequate flow, as it would not generate enough gravity pull to move waste through the system efficiently. Therefore, adhering to the 1/4 inch per foot slope helps maintain proper function and longevity of the drainage system.