What is the minimum size of a vent pipe?

The minimum size of a vent pipe is 1-1/4 inches. This size is recognized by plumbing codes as the smallest diameter that can adequately serve as a vent for residential plumbing systems. Vent pipes play a crucial role in maintaining proper air pressure within the plumbing system and preventing sewer gases from entering the living spaces.

Choosing a vent pipe size of 1-1/4 inches ensures that there is sufficient airflow to prevent siphoning and allow for the drainage system to function properly. A smaller diameter pipe might not provide adequate ventilation, potentially leading to issues such as slow drainage and unpleasant odors from sewer gases. Thus, 1-1/4 inches serves as a standard measurement that balances function and compliance with plumbing codes, ensuring safety and efficiency in plumbing systems.