In a wet vent system with seven lavatories, where is the vent connected?

In a wet vent system with seven lavatories, where is the vent connected?

• A. Most downstream fixture
• B. A random fixture in the run
• C. The fixture nearest the main stack
• D. The most upstream fixture

Answer: (D)

A wet vent uses a drainage line as a vent for other fixtures in the same run. To vent seven lavatories effectively, the vent must tie in at the most upstream fixture—the one closest to the main stack. This placement lets air reach all downstream traps as water drains, preventing siphoning and ensuring proper venting for the entire group. If the vent were placed further downstream or on a random or downstream fixture, the upstream lavatories wouldn’t be vented correctly, leading to trap siphon and poor drainage. The upstream connection guarantees the entire run is vented through a single shared vent.

A wet vent uses a drainage line as a vent for other fixtures in the same run. To vent seven lavatories effectively, the vent must tie in at the most upstream fixture—the one closest to the main stack. This placement lets air reach all downstream traps as water drains, preventing siphoning and ensuring proper venting for the entire group. If the vent were placed further downstream or on a random or downstream fixture, the upstream lavatories wouldn’t be vented correctly, leading to trap siphon and poor drainage. The upstream connection guarantees the entire run is vented through a single shared vent.