In drainage venting, which vent extends above the highest drain on the stack to allow air entry?

In drainage venting, which vent extends above the highest drain on the stack to allow air entry?

• A. Trap
• B. Fresh Air Inlet
• C. Stack Vent
• D. Rain Vent

Answer: (C)

Vent piping in a drainage system keeps trap seals from being sucked dry and helps water flow move smoothly by letting air enter as needed. The vent that rises above the highest drain on the stack serves this exact purpose: it provides a pathway for outside air to enter the drainage system, balancing pressure so traps aren’t siphoned and sewer gases are vented safely above the building. The trap itself is what seals sewer gas at a fixture, not a vent; a fresh air inlet is a different method of introducing air and isn’t the main air-entry vent above the stack; a rain vent handles roof drainage specifics and isn’t the primary stack vent.

Vent piping in a drainage system keeps trap seals from being sucked dry and helps water flow move smoothly by letting air enter as needed. The vent that rises above the highest drain on the stack serves this exact purpose: it provides a pathway for outside air to enter the drainage system, balancing pressure so traps aren’t siphoned and sewer gases are vented safely above the building. The trap itself is what seals sewer gas at a fixture, not a vent; a fresh air inlet is a different method of introducing air and isn’t the main air-entry vent above the stack; a rain vent handles roof drainage specifics and isn’t the primary stack vent.