The most common gas water heater is technically called an “atmospheric vent” type. Because warm air rises, the hot gases created by combustion are pulled by natural convection up a vertical metal flue through the roof to the outside. It’s a tried-and-true, simple system, that does not require electric power or moving parts.

   But what if the location of a water heater makes it impossible to run a vent through the roof? Then a power vent water heater is the solution. It uses an electric blower to push the combustion gases, along with added air to cool the exhaust down, through PVC pipe to an exterior wall or soffit that can be be dozens of feet away.

   There are both advantages and disadvantages to choosing a power vent hot water heater:

PROS

• Can be installed almost anywhere in a home, but best located outside the conditioned living area.

• Exhaust vent can be run horizontally for a long distance.

• Often less expensive to install for new construction, because the vent can run horizontally and terminate at an exterior wall, it does not require flashing of a roof penetration, and PVC pipe is cheaper and easier to install than metal vent pipe.

CONS

• Costs at least 50% more than a regular water heater.

• Requires more “make up” air (the air added to the exhaust flow).

• The sound of the exhaust fan may be noticeable if near or in a living area.

• 120-volt power (regular wall outlet) must be nearby for fan.

• Needs more maintenance because it has a motor and moving parts.

   A power vent water heater is recognizable by the rounded blower fan housing at the top of the tank connected to PVC pipe, like in the photo above, and below is the vent termination at a side wall. This particular water heater has more pipes connected to it than usual because it is part of a hydronic heating system—the hot water it produces is also used to heat the home. To learn more about hydronic heating, go to our blog “How does a hydronic heating system work?”  

   There are also direct vent water heaters available, which utilize a sealed system that draws air for combustion from the exterior of a home. Learn more at our blog “What is the difference between a regular water heater and a direct vent water heater?” 

Here’s links to a collection of more blog posts about WATER HEATERS:

• Are water heaters required to be raised off the floor? 

• Can a Temperature and Pressure Relief (TPR or T&P) valve be mounted to discharge horizontally?

• Where are gas water heaters not allowed to be installed?  

• Is the minimum size water heater inlet pipe 1/2" or 3/4" according to the building code?

• Can you use a light switch for a water heater disconnect? 

• How can I tell if a water heater is HUD-approved for mobile/manufactured homes?

• Can you wire a 240-volt water heater with 120 volts? 

• Is it alright to have a shut-off valve on both the hot and cold water pipes at a water heater?  

• What is the minimum clearance to doors and windows for an outdoor tankless gas water heater? 

• What is required clearance for access and working space in front of an electric water heater? 

• Why is the water heater older than the house? 

• Does a water heater need a shut-off valve? 

• Why should a tankless water heater have an isolator/service valve kit installed?

• When was a gas water heater first required to be elevated 18 inches above a garage floor?  

• Can the temperature and pressure relief (TPR) valve discharge pipe for a mobile/manufactured home water heater terminate under the home? 

• What is the purpose of a thermostatic mixing valve above a water heater? 

• Does a tankless gas water heater still work with no electricity during a power outage?  

•  Why do water heaters have a sacrificial anode? 

• What is the difference between a manufactured/mobile home water heater and a regular water heater? 

• Does a tankless water heater require a pressure relief valve?

• When is a water heater drain pan required?

   Visit our WATER HEATERS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.