What is the size of the vent header mentioned?

• A. 2 inches
• B. 4 inches
• C. 3 inches
• D. 1 inch

Answer: (C)

The size of a vent header is chosen to provide enough cross-sectional area to carry the combined air from all vent connections without creating excessive resistance or siphonage. In the scenario described, the number of fixtures connected to the header requires a middle-sized diameter to balance capacity and practicality. A 1-inch or 2-inch header would be too small for multiple vents, risking trap siphonage and poor venting, while a 4-inch header would be larger than needed for the given load and more costly. Therefore, 3 inches is the appropriate choice because it matches the required venting capacity for the described number of connections, aligning with typical code tables that scale header size with the number of fixtures.