What is the minimum slope for a horizontal waste pipe as per the plumbing code?

The minimum slope for a horizontal waste pipe as stipulated by plumbing codes, including the Massachusetts Plumbing Code, is 1/4 inch per foot. This specific slope is determined to ensure that wastewater flows efficiently through the pipe without pooling or creating blockages. A slope that is too gentle may cause solids to settle out of the wastewater, leading to clogs and compromised drainage. On the other hand, a slope that is excessively steep could cause turbulence, allowing the liquid to flow too rapidly and not carrying solids effectively. Therefore, the 1/4 inch per foot is a balanced requirement that promotes proper drainage and function of waste piping systems, ensuring both efficacy and compliance with plumbing standards.