How & why to vent your gas water heater: Options, safety tips & more

Without adequately venting your gas water heater, harmful gases like carbon monoxide could accumulate in your home and pose a severe health risk. Whether you’re installing a new water heater or replacing an old one, you’ll need to familiarize yourself with water heater venting requirements to get the most out of your unit. Let’s unpack the reasons why your water heater needs to be vented, how to properly vent it, and the venting options available to you.

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Important: The information provided in this article may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

Why does my gas water heater need to be vented?

Electric water heaters don’t require venting since they don’t produce combustion gases, but gas water heaters — whether propane or natural gas — must have a proper venting system installed. 

Gas water heaters produce combustion gases that include odorless carbon monoxide, which is dangerous and potentially fatal if the unit isn’t vented properly. Properly venting your unit helps expel these gases outside your home.

Here’s why venting is required for gas water heaters:

• Prevents gas buildup that could lead to poisoning or explosion.
• Keeps the unit running efficiently and increases its lifespan
• Complies with safety regulations and building codes

Types of water heater venting options

There are several methods to choose from when venting a gas water heater. Your choice will ultimately depend on the type of water heater you have and the layout of your home.

Atmospheric vent 

The atmospheric vent water heater is one of the most common and simplest venting systems. This system relies on natural air currents to draw combustion gases through a vertical vent pipe and expel them outside.

Advantages:

• Simple
• Cost-effective
• Ideal for homes with an existing chimney or vertical venting path

Disadvantages:

• May not work efficiently in homes that struggle with maintaining airflow
• Requires vertical venting, which limits where the water heater can be installed

Power vent

A power vent water heater uses a fan or blower to expel combustion gases through a horizontal vent. This system tends to be more flexible in terms of installation since it doesn’t rely on natural airflow.

Advantages:

• Can be installed in spaces where vertical venting isn’t possible
• Tends to be more energy-efficient than atmospheric venting

Disadvantages:

• May be more expensive due to the need for a blower motor and the electricity to run it

NOTE: A propane or natural gas power vent water heater requires the following:

• The blower must be installed in an easy-to-access location that allows for maintenance. The blower shouldn’t be against any other object.

• A dedicated electrical outlet to power the blower is needed for a power vent model.

• Only use PVC, CPVC, or ABS vent pipes since metal pipes may corrode from the condensation caused by the exhaust gases.

Direct vent

A direct vent water heater draws air from outside your home and expels the combustion gases back outside through a sealed pipe. This is ideal for homes with limited ventilation inside the living space.

Advantages:

• A sealed system prevents air inside the home from being used for combustion
• A generally safe and efficient option for tight spaces

Disadvantages:

• Requires careful installation to ensure a proper seal
• More expensive than traditional venting options

How to vent a gas water heater

If you want to safely use your gas water heater, you’ve got to make sure that it’s vented correctly. Follow these steps for a safe and successful installation.

1. Choose the right venting option

Before you begin, you’ll need to determine the type of venting system you need based on your water heater and home layout. For example, if you’re venting a gas water heater through a wall, a power vent water heater might be the best choice.

2. Install the vent hood or vent cap

Every gas water heater needs a water heater vent hood or vent cap to direct exhaust gases through the vent pipe. These caps prevent backdrafts, which could force dangerous gases back into your home.

3. Install the vent piping

Once you’ve installed the vent hood, you’ll need to attach the appropriate vent piping. Use a galvanized steel for atmospheric venting and PVC for power vent water heaters. Make sure all connections are secure and properly sealed to prevent gas leaks.

For vertical venting: If you’re venting through a chimney or roof, make sure the vent pipe has a continuous upward slope to facilitate the natural escape of gases.

For horizontal venting: When venting a gas water heater through a wall, make sure the pipe maintains a slight downward slope to allow for condensation to drain.

4. Secure and test the system

Once the piping is installed, you’ll need to secure it in place with brackets. 

When everything is set, test the system to make sure it works correctly without any leaks. If you installed a power vent system, you’ll need to make sure the blower works properly.

How to maintain your gas water heater venting system

You should periodically inspect your gas water heater’s ventilation system every 3-4 months to make sure everything looks good and is working properly. Here are a few tips.

• Inspect the vent cap and piping for any debris, such as leaves or bird nests, that could block gas flow. Remove any debris that you find.
• If you notice rust or corrosion on metal vent pipes, replace them immediately to prevent leaks.
• Check that the vent pipes haven’t shifted, which can cause air to flow incorrectly. Move them back to the correct position if needed.

Frequently asked questions

Get answers to some of the most common questions about water heaters.

Do electric water heaters need to be vented? 

No. Electric water heaters don’t produce combustion gases, so they don’t require venting. Gas models are the only ones that should be vented.

How do I vent a gas water heater through a wall? 

Venting a gas water heater through a wall typically requires a power vent system, which uses a blower to push the gases through horizontal PVC or metal pipes.

Can I install a power vent on any gas water heater? 

No. Only water heaters specifically designed for power venting should have a blower installed.

Additional information

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