For a 6-inch vent with a vertical run of 20 feet, the maximum horizontal length of a 6-inch single-wall connector is 15 feet.

• A. 20 feet
• B. 10 feet
• C. 25 feet
• D. 15 feet

Answer: (D)

In venting practice, the horizontal length of a single-wall vent connector is limited by the vent diameter and how high the vent rises. This keeps the draft strong enough and minimizes pressure losses and moisture buildup inside the connector. For a six-inch vent with a twenty-foot vertical rise, the standard table sets the maximum horizontal length of the single-wall connector at fifteen feet. Going longer would reduce draft and increase the chance of condensation or backdraft, while shorter lengths stay within the tested and approved limits. If more horizontal distance is needed, you’d change the setup (such as increasing vertical rise, using a different type of connector, or adjusting the vent design) to stay within code requirements.