What size pipe is used to dual vent two toilets?

What size pipe is used to dual vent two toilets?

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

Answer: (B)

Two inches. The vent pipe for a toilet is typically 2 inches in diameter, and this size is commonly used even when two toilets are vented together. The vent must be large enough to admit air and prevent siphoning; 1 1/2 inches or 1 inch is too small, while 3 inches is usually more than what's needed unless there are many fixtures or longer vent runs involved. In standard residential setups for two toilets, a 2" vent adequately handles the required air flow and fixture units.

Two inches. The vent pipe for a toilet is typically 2 inches in diameter, and this size is commonly used even when two toilets are vented together. The vent must be large enough to admit air and prevent siphoning; 1 1/2 inches or 1 inch is too small, while 3 inches is usually more than what's needed unless there are many fixtures or longer vent runs involved. In standard residential setups for two toilets, a 2" vent adequately handles the required air flow and fixture units.