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Do Heat Pump Water Heaters Need to Be Vented? Gas vs. Heat Pump Venting Requirements
Water heater venting can be confusing, especially when you're comparing different types of systems. If you're looking at gas water heaters, you'll need to understand which venting setup works with your home's layout. If you're considering a hybrid electric heat pump water heater, the good news is that they don't need the same kind of venting that gas units require.
Choosing the correct venting materials will help ensure your water heater operates safely and efficiently. Heat pump units just need enough space for air to circulate around them, while gas water heaters require proper venting to remove exhaust gases from your home. We'll first cover the different gas water heater vent configurations, then explain why heat pump water heaters have much simpler requirements.
Consult a professional plumbing contractor to determine the best vent configuration required for your water heater.
Standard Atmospheric Vent
Standard atmospheric water heaters are the most common type of residential gas water heaters. Working on the principle of hot air rising, atmospheric gas water heaters vent their exhaust through a vertical or upward sloping metal duct vent to exit the home. This venting may either be dedicated to the water heater or can be shared with other atmospheric vent appliances, such as a furnace. The venting must be vertical or upward sloping so that the hot exhaust rises up through the venting to exit your home.
Making sure that your home has a properly working vent system is imperative when installing a standard atmospheric vent with your water heater. Any blockages or misalignments in your home's venting may result in excess heat and fumes being released back into the ambient air. We recommend that you consult a professional plumbing contractor for installation.
Power Vent
A. O. Smith power vent gas water heaters are equipped with an electric blower fan that is installed on top of the water heater, which requires an electrical outlet to be close to the water heater. The blower pushes the exhaust and excess heat through the exhaust venting. The venting can run either vertically or horizontally with a longer line to help with space and sizing issues within your home, which makes power vent water heaters more flexible to install.
Power vents are a more efficient option, as they are designed to utilize heat from the exhaust to heat water for energy savings. Thanks to lower exhaust temperatures they allow for PVC piping, which is a less expensive solution than a standard atmospheric vent metal piping and easier to assemble. We recommend that you consult a professional plumbing contractor for installation.
Direct Vent
Direct vent gas water heaters are a type of gas water heater best suited for use when there is insufficient ventilation within the installation space in your home. A direct vent water heater draws air for combustion from outside your home rather than inside. The exhaust gasses and excess heat produced by your water heater are then vented back outdoors.
A direct vent water heater uses special coaxial venting that has separate chambers for intake air and exhaust in a single assembled vent piece. The venting runs from the water heater through the side of your home. They pull and push air from outside to negate any backdrafting within your home. This can help minimize safety risks when installing and using a gas or liquid propane tank water heater. We recommend that you consult a professional plumbing contractor for installation.
Power Direct Vent
Power direct vents are used when the space in which you are installing a water heater lacks sufficient air for combustion and requires flexibility around the installation. Consult a professional plumbing contractor to make sure that you need power direct venting before going down this installation path.
Much like direct venting, power direct venting uses a blower to pull in air from outside your home for combustion and funnels it directly to your water heater. The same blower is also used to release the combustion exhaust gasses back outside of your home. Similar to the power vent design, a power direct vent water heater can utilize PVC piping to reduce installation costs. It is important to note that they also require an electrical outlet near the water heater for installation.
Concentric Vent
Concentric venting describes any coaxial "pipe in pipe" venting design where the intake air and exhaust gas both vent through a shared assembly. It can provide an aesthetic installation with a single wall or roof penetration.
Concentric venting may be used with several types of water heaters, including direct vent, power direct vent, and tankless water heaters. However, the material of the concentric venting may be different depending on the water heater.
Concentric venting may be used for the full vent run (from water heater to outside of the home) for certain models that are exclusively designed for concentric venting, such as a direct vent water heater or concentric vent tankless model. A concentric vent termination may be used on a power direct vent tank or tankless water heater to get the same benefit of a single wall or roof penetration with an aesthetic vent termination.
In that installation separate intake and exhaust vent pipes are run between the water heater and interior wall, and only the wall penetration and termination are concentric piping. We recommend that you consult a professional plumbing contractor for installation.
Concentric Vent Termination
Concentric Vent Full Run
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Do Heat Pump Water Heaters Need to Be Vented?
Now that you understand gas water heater venting requirements, let's look at heat pump water heaters, which work completely differently. Heat pump water heaters don't need to be vented like gas water heaters because they don't burn fuel or create combustion gases. Instead of creating heat like regular electric water heaters, heat pump water heaters pull warmth from the air around them. This means they need adequate space and air circulation, but they don't need the same type of venting systems we just covered for gas water heaters.
How Heat Pump and Gas Water Heater Venting Differs
The venting requirements between these two types of water heaters are completely different:
- Gas water heaters burn fuel, which creates combustion gases that must be safely removed from your home through dedicated venting systems. These exhaust gases require proper ventilation to the outside as a safety measure.
- Heat pump water heaters don't burn anything, so they produce no combustion gases. Instead, they need adequate air circulation to pull in ambient air and release the cooler air that results from the heat-extraction process.
- Gas units require venting systems with specific materials and precise installation to remove exhaust gases from your home safely. These systems may be vertical or horizontal in tandom with an exhaust blower, depending on your home's layout and the type of gas water heater.
- Heat pump units need sufficient air volume and good air circulation, but no exhaust venting from combustion gas. The main requirement is having enough space for proper air movement around the unit.
- Gas venting involves dedicated exhaust systems that route exhaust from combustion gases outside through walls or roofs, with installation requirements that vary by home layout.
- Heat pump installation focuses on air space, which means finding a location with adequate room for air circulation, typically in basements, garages, or utility rooms.
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Frequently Asked Questions
Venting requirements depend on your water heater type. Standard atmospheric vents must be vertical or upward sloping so hot exhaust rises naturally through metal ducts. Power vent models use an electric blower and require an electrical outlet, allowing horizontal or vertical venting. Direct vent water heaters need coaxial venting with separate intake and exhaust chambers, drawing combustion air from outside. All systems must be properly installed without blockages to prevent dangerous fumes from entering your home. Professional installation is essential for safe operation.
Venting materials depend on your water heater type. Standard atmospheric vents require metal piping for high exhaust temperatures and must run vertically. Power vent and power direct vent models can use PVC piping due to lower exhaust temperatures. Direct vent systems use coaxial venting with separate intake and exhaust chambers in one assembly. Concentric venting uses a "pipe in pipe" design for cleaner installation. Always consult a professional plumbing contractor to determine correct venting materials for your specific model.
Venting codes for gas water heaters vary by location and are established by local building authorities. These codes ensure proper installation for safety and efficiency, covering vent material, sizing, termination clearances, and slope requirements. A professional plumbing contractor is familiar with local codes and national standards for your specific installation. They can determine the correct venting configuration and ensure compliance with all applicable regulations during installation.
Not all gas water heaters need roof venting. Standard atmospheric vents typically run vertically through the roof because they rely on hot air rising naturally. However, power vent and direct vent models offer more flexibility and can vent horizontally through an exterior wall rather than the roof. Power direct vent systems also allow horizontal wall venting. This flexibility makes these models easier to install where roof venting is difficult. Consult a professional plumbing contractor to determine the best venting configuration for your home.
Heat pump water heaters don't need traditional venting like gas water heaters because they don't produce exhaust from combustion gases. They do need adequate air circulation space—at least 450 cubic feet. Without enough space, the system can't operate effectively. Shop A. O. Smith heat pump water heaters to see models designed for different space requirements.
Certain gas water heaters can be vented horizontally through side walls using power vent, direct vent, power direct vent, or concentric vent systems. This gives you more options for where you can install the unit, though you'll need specific parts and professional installation. A professional installer can help you evaluate the advantages and disadvantages of different venting configurations to determine what works best for your home.
Backdrafting happens when exhaust gases from gas water heaters flow backward into your living space instead of going outside. This creates a significant safety concern because those gases may contain carbon monoxide. It usually occurs from blocked vents, inadequate draft, or negative pressure in your home. This is why many setups require a power vent to vent toxic gases outside the house safely.
Why A. O. Smith?
A. O. Smith is a leading manufacturer of both residential and commercial water heating technologies, including the #1 most specified commercial water heater.
For more than 145 years, we’ve developed state-of-the art products that push new boundaries and improve the lives of our customers.
We combine cutting-edge technology with committed people who take pride in providing the very best support for our customers.
Our products are put through rigorous quality and endurance testing so no matter where hot water is needed, A. O. Smith can provide a solution you can count on.