How far must a plumbing vent extend above the roof according to the plumbing code?

In the National Plumbing Code of Canada, the requirement for how far a plumbing vent must extend above the roof is set at a minimum of 300 mm (12 inches). This height is important for several reasons, primarily to ensure that the vent is adequately positioned to prevent the accumulation of snow, ice, or other debris which could obstruct airflow.

Vent pipes must extend high enough to avoid being affected by wind turbulence and to allow for the proper functioning of the plumbing system by facilitating the venting of sewer gases and allowing air to enter the drainage system. The specified minimum height helps maintain efficiency and safety in plumbing installations. An extension of 300 mm above the roof line provides a practical and effective solution to these issues while aligning with standardized building practices and safety regulations.

Thus, the answer of at least 300 mm is aligned with both the safety concerns and the operational requirements of a plumbing system as mandated in the plumbing code.