An apprentice is installing a new high-efficiency condensing furnace and needs to connect its condensate drain to the building's DWV system. Which of the following is the most appropriate method to prevent flue gases from entering the living space through the DWV system?

Question: An apprentice is installing a new high-efficiency condensing furnace and needs to connect its condensate drain to the building's DWV system. Which of the following is the most appropriate method to prevent flue gases from entering the living space through the DWV system?

Answer options:

• Connecting directly to a stack vent without a trap. ✅ Connecting indirectly to a floor drain equipped with a trap.
• Connecting directly to a fixture branch drain without a trap.
• Using a trap primer on the condensate connection.

Correct answer: Connecting indirectly to a floor drain equipped with a trap.

Explanation: Condensate from a high-efficiency furnace is acidic and often contains flue gases, so it must be indirectly connected to the DWV system, typically through an air break over a trapped receptor like a floor drain or laundry tub. Directly connecting without a trap would allow sewer gases into the furnace, and potentially flue gases into the living space. A trap primer is for keeping existing traps sealed, not for creating an indirect connection or managing flue gases.