What is the primary function of a vent stack in a building's drainage system?

What is the primary function of a vent stack in a building's drainage system?

• A. Vent sewer gases and allow air to prevent trap siphonage.
• B. Filter solids from wastewater.
• C. Increase water pressure in fixtures.
• D. Provide access for cleaning pipes.

Answer: (A)

Vent stacks provide a path for air to enter the drainage system and for sewer gases to escape to the outdoors. This air intake prevents negative pressure from forming as wastewater flows, which protects trap seals from siphonage and keeps odors from entering the building. The function isn’t to filter solids, increase water pressure, or serve as the main access point for cleaning; those roles are handled by other components like filters, pressure design, and cleanouts.

Vent stacks provide a path for air to enter the drainage system and for sewer gases to escape to the outdoors. This air intake prevents negative pressure from forming as wastewater flows, which protects trap seals from siphonage and keeps odors from entering the building. The function isn’t to filter solids, increase water pressure, or serve as the main access point for cleaning; those roles are handled by other components like filters, pressure design, and cleanouts.