Water Heater Venting 101: Everything You Need to Know
Keep your home and family safe with good water heater venting
Highlights
Gas and propane water heaters require a water heater venting system.
Water heater venting systems remove dangerous gases from inside a home.
The three types of venting are atmospheric, power, and direct venting.
Backdrafting is the biggest risk associated with venting.
The safest way to install or repair venting is to hire a professional.
Some of us take hot water for granted—until it’s gone. Good maintenance of your water heater's key components is very important to keep it working as it should. For gas or propane water heaters, one of the most critical items is the water heater venting system.
Water heater venting helps prevent carbon monoxide buildup and ensures your water heater operates at the highest level. Keep reading to learn more about these systems, how they work, and why they’re important.
What is Water Heater Venting?
Gas and propane naturally create dangerous gases like carbon monoxide. Without a water heater venting system, these gases could accumulate in your home and become dangerous (called backdrafting).
Water heater venting systems work via a vent duct or pipe that moves exhaust gases outdoors. They either rely on natural convection or fans to move the gases out so they don’t pose a risk to your home.
Not only that—proper venting also helps maintain the efficiency of your water heater. So if you want to avoid having to take cold showers and like having lower electricity bills, it’s important that you make sure your water heater venting works how it’s supposed to for as long as it’s supposed to.
Backdrafting: The Biggest Water Heater Venting Concern
Backdrafting is a dangerous situation that can occur when a gas-fired appliance, such as your water heater, doesn't have proper ventilation. This can create a potentially life-threatening situation, as the gases can include carbon monoxide, a colorless and odorless gas that can be deadly in high concentrations.
The best way to prevent backdrafting is to maintain your water heater and its venting system. Doing so will help ensure every component works how it should to keep your family and system safe.
You can also take additional steps to catch backdrafting if it does occur, like buying a carbon monoxide detector and installing it near your water heater.
Signs Your Water Heater May Be Backdrafting
In the event of backdrafting, you may experience headaches, dizziness, and nausea. There are also signs you should look for in your home or near your water heater, such as:
Dense, black smoke that turns a greyish-yellow
Excessive heat buildup
Little or no visible flame
Melted plastic on your draft hood
Condensation pooling at the top of the tank or on the cold water pipes
Corrosion at the top of your water heater tank
If you suspect your water heater is malfunctioning or have concerns about the ventilation in your system, schedule a visit from a local water heater contractor immediately. Backdrafting can be dangerous if not handled properly and quickly.
Other Reasons Why Water Heater Venting Is Important
In addition to backdraft risks, a poorly vented water heater poses a number of other risks for a household. While some reasons to properly vent your water heater protect your health, others can simply help you avoid unnecessary repair or replacement costs. Here's a look at the top three reasons why water heater venting is important:
1. Overheating: Improper venting can cause a water heater to become overheated to the point that it is damaged beyond repair.
2. Warranty Protection: If your water heater malfunctions, any manufacturer warranty that is still in place may be voided if it wasn't properly installed with adequate venting.
3. Malfunction: Improper venting can cause a water heater to malfunction based on the lack of oxygen needed for combustion.
Types of Water Heater Venting
There are three main types of water heater venting: atmospheric venting, power venting, and direct venting. Each type has its own benefits and drawbacks, and ultimately the one you choose depends on a few factors, such as:
Placement
Type of water heater
Building codes
Budget
Water heater’s BTU input
It’s not easy to pick the right one for your home. You should consider working with a licensed professional to help assess your options.
Atmospheric Venting/Chimney Venting
You’ve probably heard the saying, “Hot air rises.” Atmospheric or chimney venting takes advantage of that natural convection. It relies on buoyancy to push combustion gases from your water heater through a flue or chimney pipe and vent them outside.
Atmospheric venting is the most common type of water heater venting. But, if there's a change in air pressure, like during high winds, it can disrupt the natural flow and cause combustion gases to spill back into the home.
Best for: Most homes as long as the weather isn’t a significant variable.
Power Venting
Power venting is a more active approach to venting. It relies on a fan or blower to remove combustion gases and is often used when natural convection venting isn't possible, like in basements.
It’s also the method most often used for high-efficiency water heaters, which usually don’t produce a hot enough exhaust gas that can rise naturally through a flue pipe, requiring the support of a blower or fan.
With this configuration, the fan or blower is mounted on top of the heater’s draft hood, allowing for more installation flexibility. It can be installed horizontally or vertically across short or long distances but does need access to a power source.
Best for: Homes that require more flexibility with heater installation.
Direct Venting
Direct venting uses intake and exhaust pipes to bring in and vent combustion gases. Together, these pipes create a fully sealed combustion system that prevents gases from escaping into the home.
They work with the same type of natural convection as atmospheric venting but within a closed system. Because of this, they’re more complicated and expensive to install.
Direct venting is most often used when there is no access to a vertical vent termination point, such as in townhomes or multifamily buildings. Some building codes may also require it for safety purposes.
Best for: Places that don’t have access to the outside for exhaust.
Common Venting
There are also systems, called common vent configurations, that move the gases to another system that utilizes gas (like a propane furnace). However, many code jurisdictions have severely limited the use cases for these systems due to the risks involved.
If your current venting is a common vent configuration, you’ll likely need to consider a replacement rather than a repair to be up to code.
DIY vs. Hiring a Pro
Installing water heater venting is not a job for the average homeowner. Unless you have previous experience working with water heater installation specific to your desired model, you should leave the job to a trustworthy pro.
A licensed and insured water heater installation pro charges $500 to $1,000 on average to install venting. The final price may depend on the venting configuration and water heater model. For example, traditional water heater venting may cost between $900 and $2,500, whereas tankless water heater venting costs from $1,000 to $3,500.
Questions to Ask a Water Heater Pro
If you're noticing any signs of trouble with your water heater's venting, you should contact a pro immediately to get a diagnosis. In order to choose the right professional, it's important to ask the right questions. Here's a look at the core questions to ask a water heater pro during the initial phone call or at-home inspection:
How many years have you been in business?
Are you certified and licensed to work on my specific type of water heater?
Do you offer a work warranty?
Is your company bonded and insured?
Are you able to provide replacement water heater components the same day after diagnosing the issue?
Is my current water heater the optimal choice for my home?
Can you provide comparative quotes to help me get an idea of water heater replacement cost versus the cost to fix my current one?
Can you confirm that my water heater is safely vented according to the latest codes and safety standards?
Are there maintenance tips I can use to prevent this issue from happening again?
Can you help me to improve my water heater's efficiency?
Frequently Asked Questions
Not all types of water heaters require a venting system. Electric tankless water heaters don’t use natural or propane gas, so no venting is required. Instead, they use electric burners to heat water quickly and efficiently. However, any system that does use gas or propane will require ventilation.
The right way to vent a gas water heater is to have a pipe directly upward or slopes upward out of the house. Because hot air naturally rises, this type of venting will efficiently ensure that all gas moves out of the house. Your system may rely on fans or blowers as well.
You can and should vent the gas from your hot water heater to the outside of your home. Traditionally, these gases were vented back to other gas appliances, like stoves or furnaces, but many jurisdictions have outlawed this practice due to the risks it provides.
Most water heaters today use atmospheric venting that exhausts the gas out of the home through a pipe.
If your system is not vented properly, you could experience what’s called backdrafting. Backdrafting is when your ventilation system isn’t working as it should, and instead of releasing gases outside, they get trapped inside your home.
Gas and propane water heaters create a few types of combustion gases, but the most dangerous is carbon monoxide. If there’s too much build-up of these gases inside your home, it can lead to carbon monoxide poisoning.
Some of the telltale signs of backdrafting include moisture on or around your water heater, corrosion stains on top of the water heater, or dark smoke or soot. You may also experience signs of carbon monoxide poisoning, like a headache or nausea.
To check if it’s backdrafting, you can hold up a small mirror near your draft hood. If it gets foggy, there is moisture in your air. You can also cup your hands around the hood to see if you feel the moisture. Either way, you should contact a water heater repair professional immediately.