What is the minimum slope required for a horizontal drain pipe sized between 3 and 6 inches?

The correct minimum slope required for a horizontal drain pipe sized between 3 and 6 inches is 1/4-inch per foot. This specific slope is mandated to ensure that wastewater flows properly through the pipe without stagnation. Insufficient slope can lead to blockages, as waste may not be carried away effectively, while excessive slope can cause the liquid to flow too quickly, not allowing solids to be carried along efficiently.

In plumbing codes, such as the Uniform Plumbing Code (UPC) and others, a slope of 1/4-inch per foot is typically required for pipes of this diameter to maintain optimal flow dynamics and prevent drainage issues. The establishment of this minimum slope serves to facilitate effective waste removal and helps mitigate the risk of clogs in the drainage system.