How Do Power Vents Work?


Power vents are commonly found in water heaters and fireplaces. They are an efficient and practical method to vent burnt combustion gases from the house and can eliminate dangerous backdrafting, which occurs when air flows backward down a chimney or pipe. Power vents give the homeowner more options in both new construction and remodeling projects.


  • Burning fuel in a water heater or fireplace produces combustion gases that have to be expelled from the house. A power vent uses a small electric blower to force the burnt gases outside the house through a flue. The other alternative is to allow the combustion gases to flow outside using a natural draft, which relies on the tendency of warm gases to rise. With a power vent system, combustion air for the water heater or fireplace is drawn by natural draft from inside the house.

Water Heaters

  • A power vent on a water heater can exhaust the combustion byproducts through a vertical flue or horizontally out through an adjacent outside wall. This creates more flexibility in the location of the water heater. The blower fan generates a slight vacuum to draw combustion air into the burners, which slightly increases fuel efficiency.


  • A fireplace normally vents through a chimney, but also can have a power vent or natural draft exhaust vent. A power vented fireplace can be placed just about anywhere in the house; a chimney is not always necessary. Vent piping is more versatile with a power vent. It can go directly through an outside wall or can make several turns from more difficult locations to get outside.


  • With natural draft exhausts, there is always the danger of combustion gases backdrafting into the house. With a power vent fan, the exhaust gases are forced out of the house, thereby preventing any possibility of a backdraft. This allows the homeowner to operate a clothes dryer and a kitchen range hood at the same time without worrying about carbon monoxide buildup.


  • Since a power vent has an electric blower, it will not operate in the event of a power failure. Because the fan has mechanical parts, it eventually will fail and need to be repaired or replaced. A water heater with a natural exhaust flue or a fireplace with a chimney does not have mechanical parts and requires very little maintenance. A power vent fan sometimes can be noisy, so they should be located either outside the house or in an area where the noise can be isolated.

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  • Photo Credit roof vent image by hazel proudlove from Shower image by Semfamily from fireplace image by askthegeek from
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