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Direct Vent Water Heaters vs. Power Vent Water Heaters

Updated
Four key differences you should know about.

When choosing a new water heater, one of the main decisions will be a direct vent water heater vs a power vent water heater. Selecting the right exhaust fan for your hot water heater will determine how hot air is removed from your home as waste.

Unless you have a lot of experience with heaters, these two terms will probably need some explaining. Each of the two types is more suitable in certain situations.

In this article, we will explain the differences between direct vent water heaters and power vent water heaters. This will give you a better understanding of power vent vs direct vent, so you can choose the ideal heater for your needs.


Hot Water Heater Basics

Water heaters that burn natural gas, propane, or oil require a venting system. This is because the fuel that is burned to heat your water releases byproducts including carbon monoxide, which is highly poisonous (1).

The venting system is responsible for safely removing these dangerous gases from your home. Different water heaters have different types of ventilation. These include an atmospheric or standard vent, direct vent, power vent, and others.

In this article, we will compare direct vent water heaters against power vent water heater.

Direct Vent Water Heater

For combustion to occur, the heater requires air, which can be drawn from inside or outside your home. Direct vent water heaters draw their air from outside, combustion takes place, then the waste gases are sent back outdoors.

Some models have a large flexible pipe that runs from the heater, through a nearby wall to the exterior of the house. Inside the large pipe, there will be a smaller pipe that channels waste gases outside.

Other models have two flexible pipes — one for air supply and the other for hot air removal. This type of venting provides a sealed system with no possibility of backdrafting.

What is Backdrafting?

Backdrafting occurs when hazardous gases move in reverse through the vent pipe. These harmful gases find their way into living spaces and can be fatal to anyone who comes into contact with them.

Hot air is lighter than cool air and as a result, it rises through the flue and leaves the home. However, there are certain situations when the indoor air pressure becomes too low.

This can be caused by air being expelled at a fast rate by dryers, fans, and fireplaces. The low indoor pressure causes harmful gases to be sucked back into the house.

Backdrafting occurs as a result of poorly configured flues and blockages within the flue (2).

Power Vent Water Heater

Power vent systems take their combustion air from your home. They use a fan or blower to expel gases through a sealed vent that is installed horizontally. The gases can also be expelled vertically via a pipe to the roof.

Power vents shouldn’t be confused with power direct vents. The latter type uses two pipes — one for taking air from outside and the other for expelling waste gases (3).

As power vents draw their air from indoors, they need to be located in an area that enjoys good airflow. As with direct vent water heaters, power vent units also use a sealed system to prevent backdrafting.

Direct Vent vs. Power Vent: What Are the Differences?

Here are some of the key differences to help you choose the best venting system for your home:

1. Heater Location

Direct vent heaters should be placed a recommended four feet from an adjacent wall, as they use natural airflow. The distance can vary depending on building codes or the model (4). Power vents have longer flues that can reach up to 40 feet.

If your direct vent uses a chimney to expel air, you will need to have the heater located near one. Power vents don’t use chimneys but need to be in rooms with adequate airflow.

2. Operational Costs

You may find that a power vent water heater increases your energy bill because electricity is required for the fan to function. This is not the case with direct vents that operate using the principle of hot air rising over cool air.

Installation costs of a power vent heater are also much higher. You will need to factor in the cost of the fan and pipes among your other expenses. If you’re looking for a budget-friendly option, a direct vent water heater system is worth considering.

3. Noise

Power vents produce some noise while the fan is running. This occurs whenever the water heater is in operation. It may not be enough to distract you, but it’s worth keeping in mind.

As direct vents ‘breathe’ in and out naturally, there is rarely any noticeable noise from them.

4. Efficiency

Power vents are far more advanced than their direct vent counterparts and will provide multiple benefits, including higher energy efficiency and venting flexibility.

Even so, it’s worth remembering that power vent water heaters require electricity to function. You can expect to receive a higher electric bill as a result.

FAQs

What Is a Direct Vent Water Heater?

A direct vent water heater draws in air from outside, uses it during the combustion process, then vents the dangerous waste gas that is created back outdoors. This means it requires two pipes, which are either separate pipes or a smaller pipe inside a larger one. This creates a sealed system that prevents backdrafting of dangerous gases from occurring.

What Is a Power Vent Water Heater?

A power vent water heater draws air from its surroundings inside your home, uses it for combustion, then vents the waste byproducts outside via a pipe. This means they need to be positioned in an open area with good air circulation. It only has one pipe, which is sealed to prevent backdrafting, as long as it is installed properly.

Can I Replace a Power Vent Water Heater With a Direct Vent?

You should be able to replace a power vent water heater with a direct vent water heater, as long as you replace the pipes that will be used to draw in air and vent the toxic byproducts of combustion. Replacing a direct vent with a power vent might not be possible, as you need to ensure you have sufficient space and airflow around a power vent heater.

Does a Gas Water Heater Need To Be Vented?

A gas water heater needs to be vented because of the byproducts that are created during the combustion process. Some of the gases that are created, including carbon monoxide, can be fatal if they come into contact with people, so it is critical that they are safely vented outside. This is why it is so important to have your gas water heater installed and serviced by a professional.


Which One Is Better?

It’s difficult to say that a direct vent water heater or power vent water heater is better overall, as this depends on your requirements, where you live, and building codes where applicable.

Ultimately, both venting solutions provide a sealed system, which is very important. It’s up to you to decide which of these gas water heater venting options will be more suitable for your home.

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About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.