What is the maximum allowable distance for a vent from a fixture trap according to the code?

The maximum allowable distance for a vent from a fixture trap, according to the Massachusetts Plumbing Code, is 6 feet. This requirement is designed to ensure that the plumbing system operates effectively by preventing the buildup of negative pressure in the drainage system, which can lead to the siphoning of traps and the potential release of sewer gases into the building.

By maintaining a maximum distance of 6 feet between the trap and its corresponding vent, the code ensures that the vent is close enough to the fixture trap to allow for proper airflow and pressure equalization. This helps to maintain the necessary water seal in the trap, thereby preventing odors and gases from escaping.

In practice, if the vent is too far from the trap, it may not provide sufficient air to prevent siphoning action, which can result in plumbing issues and create health hazards. The choice of 6 feet strikes a balance between practicality and functionality within residential and commercial plumbing systems.