What minimum slope is required for horizontal drain pipes of 3 inches in size?

The minimum slope required for horizontal drain pipes of 3 inches in size is 1/4 inch per foot. This standard is established to ensure that wastewater flows smoothly through the pipe without stagnation. A slope that is too shallow, such as 1/8 inch per foot, may lead to blockages and buildup of solids, which can compromise the drainage system's efficiency. The specified 1/4 inch per foot slope promotes adequate flow velocity, allowing the waste to move effectively towards the drainage system without accumulating. Maintaining this slope is vital to adhere to plumbing codes and engineering practices, ensuring reliable drainage and reducing the risk of backups.