When is it necessary to provide a relief vent in drainage stacks?

A relief vent in drainage stacks is essential under specific conditions to ensure proper air circulation and prevent siphoning, which can lead to drain problems and potential sewer gas issues. Providing a relief vent becomes necessary particularly in buildings with numerous branch intervals, as it allows for adequate ventilation in the system.

In the context of this question, the selected answer addresses the requirement for relief vents in buildings that have more than ten branch intervals, specifically at every tenth interval. This regulation ensures that as the complexity and number of drainage branches increase, there is sufficient venting to handle the pressure changes and airflow needs that arise from such configurations.

Having relief vents at regular intervals helps maintain proper drainage function and minimizes the risk of blockages or pressure imbalances that could impair the system's efficiency. Proper design and implementation are crucial in avoiding potential plumbing issues that could arise from inadequate venting in large drainage systems.