In wet venting between two fixtures, the drain between the two fixtures must be at least one pipe size larger than the upper fixture drain and not smaller than what diameter?

In wet venting between two fixtures, the drain between the two fixtures must be at least one pipe size larger than the upper fixture drain and not smaller than what diameter?

• A. 1 inch
• B. 1-1/4 inch
• C. 2 inches
• D. 2-1/2 inches

Answer: (C)

In wet venting between two fixtures, the connection between them must be sized to carry the wastewater from the upper fixture and still function as a vent, which means the drain between them must be at least one pipe size larger than the upper fixture’s drain. At the same time, there’s a minimum diameter you must meet, regardless of the upper fixture size, to ensure proper venting and flow. That minimum is 2 inches. So the drain between the two fixtures cannot be smaller than 2 inches in diameter. If the upper fixture drain is 1-1/4" or 1-1/2", the next standard size would be at least 2", which satisfies both requirements. Options smaller than 2 inches don’t provide adequate venting, while a larger size like 2-1/2" is allowed but not required by the stated minimum.

In wet venting between two fixtures, the connection between them must be sized to carry the wastewater from the upper fixture and still function as a vent, which means the drain between them must be at least one pipe size larger than the upper fixture’s drain. At the same time, there’s a minimum diameter you must meet, regardless of the upper fixture size, to ensure proper venting and flow. That minimum is 2 inches. So the drain between the two fixtures cannot be smaller than 2 inches in diameter. If the upper fixture drain is 1-1/4" or 1-1/2", the next standard size would be at least 2", which satisfies both requirements. Options smaller than 2 inches don’t provide adequate venting, while a larger size like 2-1/2" is allowed but not required by the stated minimum.