If a vent stack terminates 4 feet from a ventilation grill, what must be done?

Raising the vent terminal to a point at least 2 feet above the ventilation grill opening is essential for maintaining proper ventilation and preventing cross-contamination of air. This requirement helps to ensure that the vent stack can effectively release sewer gases and odors without risking the entrance of contaminated air into the building through the ventilation grill.

Maintaining this height minimizes the chance of re-entrainment of the exhaust gases back into the building's air intake, which is critical for health and safety reasons. Effective ventilation is vital in plumbing systems to avoid problematic pressure changes and to facilitate proper airflow, ensuring that plumbing fixtures operate efficiently and hygienically.

The requirement does not just focus on roof height. Instead, it specifically addresses the proximity to ventilation systems that could otherwise be adversely affected. Adhering to this height requirement fosters a robust ventilation system that keeps the interior environment safe and prevents any backdraft or negative impact on indoor air quality.