American Water Heater 381T1546NOX Water Heater User Manual

Servicing should only be performed by a Qualied Service Technician
The illustration below shows the required clearances for venting units using natural draft venting.
The vent must extend at least 3 feet above the highest point where it passes through a roof of a building
and at least 2 feet higher than any portion of a building within a horizontal distance of 10 feet (for vents of 12
inches in diameter or less).