If vents exceed 40 feet in developed length, by how much should they be increased?

When vents exceed 40 feet in developed length, they should be increased by 1 nominal pipe size to ensure proper air flow and prevent the build-up of negative pressure within the venting system. This increase allows for adequate ventilation and helps to maintain the efficiency of waste removal from the plumbing system.

If the vent size is not increased appropriately, it may not effectively carry away gases or odors, leading to potential venting issues and the possibility of back pressure affecting drain function. This adjustment is standard practice in plumbing design to ensure optimal performance and compliance with plumbing codes, which emphasize the importance of providing sufficient venting for wastewater systems.

In contrast, other size increases, such as by 1/2, 1-1/4, or 2 nominal pipe sizes, are not typically required and may be excessive for the intended purpose, leading to unnecessary costs and complications in the installation while not addressing the specific needs dictated by a length exceeding 40 feet. Proper sizing is crucial for maintaining a balanced system that functions efficiently and safely.