What Is a Direct Vent Heater?

A direct vent hot water heater contains a sealed pipe system for intake combustion air and exhaust gases. This creates an air-tight combustion chamber which eliminates backdrafting and improves fuel efficiency.


Always have hot water

For combustion air, a gas-fired hot water heater draws in outside air or pulls it from inside the house.  Burnt exhaust gases are expelled through a chimney, a vertical flue or horizontally via a pipe through a sidewall.

Direct Vent

A direct vent water heater incorporates a closed horizontal piping system through a sidewall to the outside for intake and exhaust air.  This creates an air-tight combustion system.


Plumbers will install a direct vent heater when air-tight construction of a house makes it difficult for a water heater to draw sufficient combustion air from inside the house.  The horizontal design of a direct vent system avoids the problem of construction obstacles blocking the installation of a vertical exhaust vent and a chimney is not available.


The air-tight combustion chamber stops backdrafting of exhaust gases into the house.  A direct venting system improves fuel efficiency since it does not take conditioned air from inside the house.


Because a direct vent system relies on natural air circulation, the water heater must be located no more than four feet from the outside wall. 

About the Author

In 2007, Jim Woodruff began writing content for e-commerce Web sites and article directories. He specializes in business and finance. Woodruff holds a Bachelor of Mechanical Engineering from the Georgia Institute of Technology and a Master of Business Administration from the Columbia University Graduate School of Business.