What is the maximum vertical distance a vent can be installed above a fixture's flood level?

The correct answer is based on plumbing codes that establish the maximum vertical distance a vent can be installed above a fixture’s flood level to ensure proper ventilation and functionality. Specifically, a vent must be within 24 inches of the fixture’s flood level to allow effective circulation of air, ensuring that pressure changes do not disrupt the drainage system. This requirement is crucial to prevent siphoning and to maintain the trap seal, which keeps sewer gases from entering living spaces.

By adhering to this guideline, the plumbing system can operate efficiently, preventing issues like backpressure or a failed drainage system. Installing a vent more than 24 inches above the fixture can compromise venting efficiency, leading to potential malfunctions. This is why the other height options fall outside of this specific requirement, as they do not align with the standard regulations governing vent installations.