How To Vent Tankless Water Heater? Complete Guide 2022 (2023)

One of the most critical things in deploying a tankless device is how to vent tankless water heater. Correct venting of a water heating system can guarantee efficient performance and increase the lifespan of your appliance.

Selecting the tankless route for your family’s hot water needs certainly comes with countless benefits –like saving utility bills and reducing power consumption. They are highly energy-efficient, enabling you to lower energy expenses by up to 50%.

Additionally, they can decrease greenhouse gas emissions by up to 60% compared to tank-style water heating systems. You can hang them on a wall either inside or outside your residence and procure limitless water without having to wait for a long time.

However, gas and propane-fired units also have their own issues if not installed correctly, like failing very soon in their lifespan due to poor venting.

Therefore, it’s necessary to vent a tankless model according to the manufacturer’s instructions so that it can operate effectively and to prevent the hazard of carbon monoxide poisoning.

How To Vent Tankless Water Heater? Complete Guide 2022 (1)

Why Is It Vital To Vent A Tankless Water Heater?

Before learning how to vent tankless water heater, you should know why venting a heater is necessary. All water heating systems that burn gas need a venting system.

The burning process produces heat and destructive exhaust gases. They need a special venting to blow warm exhaust gas outside, where it disperses.

If you have a non-condensing device, you will need a venting of metal like stainless steel or thick aluminum as the exhaust gas is extremely hot. However, you don’t need metal venting for condensing models.

(Video) Tankless Water Heaters (COMPLETE GUIDE) | GOT2LEARN

What Are The Important Aspects Of Venting?

A tankless machine’s venting has various components, and you should know about all of them before installing venting.

Outdoor Deployment

If it’s difficult for you to install venting for your indoor device, you can opt for an outdoor heater. Search for units that are anticipated for outdoor deployment and don’t need venting.

Vent Adaptor And Exhaust

A vent adapter is required for linking the appliance to the exhaust hose. You can choose a 3in adapter or 4in adapter, according to your heater type.

The vent pipes should be made of stainless steel and approved by UL. Vent pipes made of PVC are a bad option.

How To Vent Tankless Water Heater? Complete Guide 2022 (2)

What Types Of Vents Do Tankless Water Heaters Utilize?

They use two types of vents, depending on your particular model.

Direct Venting

It draws air in from a vent pipe that goes through the external wall or the roof and then vents the exhaust gas through a separate vent duct or a separate chamber of the same pipe.

The biggest benefit of this type of vent is that it permits the heater to be installed in smaller spaces. You can use concentric or dual Rinnai tankless water heater venting for your tankless appliance.

A concentric vent draws in air and exhaust gases on the same pipe. The exhaust is in the middle so that the vent’s exterior does not warm up.

They lower the danger of accidental fires initiated by combustible exhausts around the unit. You will have to use PVC pipes because you cannot seal stainless steel with silicone.

(Video) 3 Things They Don’t Tell You About Tankless

Power Venting

A tankless water heating system with a power vent has a noiseless electric blower fan placed on the unit’s top, and it can have either horizontal or vertical vent tubes.

Since the vent does not depend on the warm air’s buoyancy, it can be run horizontally to the house’s exterior. The electric blower cools the air, so you can use PVC pipes as they are easy to assemble. There should be an electrical outlet nearby the device for powering the fan.

How To Vent Tankless Water Heater?

There are two ways to vent a tankless device: horizontal and vertical.

Horizontal Venting Installation

Horizontal venting can be installed in two ways. First, you can utilize a downward slope to deploy the vent’s adapter, 90-degree elbow, and the stainless steel vent hose. You have to get the vent duct of the right length and also maintain the exhaust outside the home’s sidewall.

You can rely on small plastic or metal cap to attach the vent’s interior along the exterior. A ninety-degree elbow is requisite for finishing the installation process.

Secondly, you can install it vertically, with an upward slope, by adding a vertical condensation trap into the elements.

Vertical Venting Installation

Vertical venting placement is much more flexible than horizontal orientation since it consists of various aspects. Nevertheless, the elements required for the plant can remain the same.

You must purchase an adapter, a ninety-degree elbow, and a condensation trap. For some heaters, you don’t need a condensation trap, whereas others have integrated condensation traps.

You need to buy stainless steel for discharging pipes to discharge the outside of your house. Furthermore, you need a fire stop for each ceiling where the appliance is ventilated through.

On the other hand, add a rain cap, a 90-degree elbow for ending the attachment, a storm collar, and a roof flashing on your shopping list.

(Video) Top 5 Best Tankless Water Heaters You can Buy Right Now [2022]

Is Combustion Air Vital For Tankless Water Heaters?

Combustion air is important for tankless models, and you must know how to deliver combustion air to your machine. Once you place your unit in an open area, combustion air will not bring wind inside your residence.

Some models can work in several atmospheres where they don’t gather fresh air outside the installation’s outer area. As a rule of thumb, a unit that relies on combustion air has to have a minimum of 10,000 cu. ft. around the heater.

The enclosed location needs air tubes and additional air inlets. The machines that require combustion air from the outdoors should have a second hose that has to be put in. It will clean air from the house’s exterior into the atmosphere where the device is installed.

How To Vent Tankless Water Heater? Complete Guide 2022 (3)

How To Install Venting Tankless Water Heater? Some Important Things To Remember

  1. Tankless devices that are installed outdoors allow you to get indoor area. Mounting a heater outside clears up indoor space and does not require extra emission.
  2. Condensation units decrease the installation cost. The exhaust vent is made of plastic or PVC pipe instead of metal, which is a feature that lowers installation expenses.
  3. Tankless machine venting style offers numerous emission choices. They blow exhaust from the heater horizontally by using fans, thus facilitating vents to end on various positions of your property.
  4. Models that have a coaxial vent style provide additional safety benefits. If any pipe begins to leak, the air stays within the coaxial vent and does not enter your residence.
  5. Recess boxes support heaters to adjust within walls without suspending the residence’s exterior. This arrangement allows them to suit inside the house’s frame and not hang from the side.
  6. Pipe covers and inventive ending points provide attention-grabbing emission solutions.

Frequently Asked Questions

Q. Is It Possible To Vent A Tankless Water Heater Through A Sidewall?

It’s not necessary to vent a heater through the roof. The vents in the tankless machine can end on a sidewall since their combustion fans blow exhaust horizontally, so the warm air goes up and out of the facility.

Q. Do Electric Tankless Water Heaters Need To Be Vented?

If you don’t want to deal with venting problems, you can consider installing an electric tankless water heater. These appliances don’t require venting and offer more options than propane and natural gas heaters.
Gallon per minute (GPM) is the major problem with them. Moreover, they are highly suitable for point-of-use applications and houses with smaller water needs.

(Video) Best Tankless Gas Water Heaters 2022 – Newest Reviews of Top 10 Best Tankless Gas Water Heater

Q. Can You Use PVC To Vent A Tankless Water Heater?

You can use ABS or PVC material for your unit with power venting. These models have an electric blower fan that cools the air and lowers the exhaust gas temperature going through the vent enough that it won’t compromise the vent.
Nonetheless, you should determine the requirements of PVC before installing one. You can install it vertically or horizontally. Before installing, you should also check if they are allowed by the heater brand and your local authorities.

Q. Can A Tankless Water Heater Be Vented Through A Chimney?

No, you cannot use a chimney for venting purposes.

Q. How Hot Does A Water Heater Vent Pipe Get?

If your device is set to deposit water at 140 degrees Fahrenheit to reduce legionella bacteria production, the flue gas temperature will be approximately 160 degrees Fahrenheit when the unit is new.
As scale gathers and the unit’s efficiency decreases, the flue gas temperature can rise up to 350 degrees Fahrenheit.

Q. Can A Gas Tankless Water Heater And Furnace Be Vented Together?

Yes, you can vent the furnace and gas unit together. This is because many houses have a tankless water heating system and furnace sharing the same exhaust vent. However, you must install a vent pipe of the right size that your appliance needs.


Proper deployment of venting is essential for the efficient functioning of your water heater and its sturdiness. How to vent tankless water heater is based on multiple factors such as fuel type, climate, safety concerns, and native codification requirements, specifically regarding the propane and gas-powered heaters which need combustion. Consequently, it’s best to employ the services of an experienced plumber to mount the unit of your choice.

(Video) Proper venting of a Rinnai tankless heater.


How do I vent my tankless water heater? ›

Tankless water heaters can vent through the roof or a side wall, creating more flexibility and options for placement. Traditional gas tank water heater require venting through the roof. Tankless water heaters use fans to blow exhaust from the unit horizontally, allowing vents to terminate on the side of a house.

Do all tankless water heaters need to be vented? ›

No. Unlike gas tankless water heaters and gas traditional tank style water heaters, electric tankless water heaters do not require any venting. This is often one of the deciding factors when choosing whether you should purchase a gas or electric tankless water heater.

Can you direct vent a tankless water heater? ›

Tankless water heaters can be vented in two ways: power-vent or direct-vent. Power-vent units use indoor air for combustion and simply vent the exhaust to the outside. Direct-vent units pull in air from the outside, so they have two vents for intake and exhaust.

Can I use PVC to vent my tankless water heater? ›

In most cases, PVC makes a great venting material. It's the least expensive option and is easy to install. And it's a good reason to consider a high-efficiency condensing unit.

Do tankless water heaters need fresh air intake? ›

Tankless water heaters work by supercharging a continuous supply of water with enough heat to supply your entire home. However, you'll also need to provide a source of fresh air to your unit to fuel the combustion engine inside. This is done through a process known as venting.

What type of vent do you need for a tankless water heater? ›

Tankless water heaters don't always need two ventilation pipes, even for direct-vent units. Direct-vent water heaters can use two separate pipes for intake and exhaust, but some manufacturers offer concentric venting, a single pipe that contains an inner exhaust vent and an outer intake vent.

Can you use galvanized vent pipe for tankless water heater? ›

The vent pipe must be made of stainless steel designed for venting corrosive gases. The standard galvanized vent from your old storage tank heater would quickly rust away if your tankless heater vented through it.

Can you use B vent on tankless water heater? ›

Type “B” gas vent can not be used on most of these heaters for this reason. Another reason this vent is required is that the vent systems are under pressure from the fan within the heater.

How close can a tankless water heater vent be to a window? ›

Indoor Installations

A tankless water heater requires a 4-foot clearance from the side or below a door or window that opens, unless the unit is directly vented to the outside, says Ernie Graves. If the water heater is installed above the door or window, it needs 12 inches of clearance.

Can tankless water heater vent vertically? ›

All indoor tankless gas water heaters must be vented vertically or horizontally to the outdoors using factory approved venting material (No other venting material is permitted).

Can you vent a tankless water heater through furnace vent? ›

When installing a tankless water heater, you have to consider the type of heater to guide you on what kind of venting you will need. Since a high-efficiency gas water heater produces corrosive combustion gases, you should avoid connecting it with the furnace vent or other existing vents for other appliances.

How far can you vent a Rinnai tankless water heater? ›

Vent lengths up to 100' with seven TWH units; 41' with 12 TWH units using 6" diameter venting. There are easy push fit joints—no cement or glue required.

Can you vent a gas water heater horizontally? ›

Power Vent

This requires an electrical outlet near the water heater. The blower forces the exhaust heat through the exhaust venting, which can be installed either vertically or horizontally with a longer line. This provides more flexibility in where the water heater is located in the home.

Can a hot water heater be vented with PVC? ›

A standard will be needed for plastic flue pipes that should include a temperature gauge and a high limit probe. Then PVC, CPVC and polypropylene flue gas piping can be safely used on high efficiency boilers and water heaters.

How high does a water heater vent need to be? ›

For a single-wall pipe, you need 6" clearance, and you cannot pass it through a ceiling, floor, or wall unless it's masonry or concrete (non-combustible). For the draft hood connection, you need to allow for at least 12" of vertical vent before throwing an elbow fitting in the line.

How much combustion air does a tankless water heater need? ›

As a general rule, water heaters need 50 cubic feet of air per 1,000 BTUs/hr.

Which is more efficient gas or electric tankless water heater? ›

The biggest difference between electric tankless water heaters and gas tankless water heaters is their efficiency. Electric tankless water heaters are typically around 98 percent or more efficient while gas tankless water heaters are around 80-85 percent efficient.

Is it normal to smell gas from a tankless water heater? ›

If you smell gas from a tankless water heater, it means there is a leak somewhere, which you need to get fixed out immediately. A tankless water heater will give out gas-only when there is a gas leak or incomplete combustion. Of course, a gas leak is hazardous, so it isn't something you should overlook.

Can you vent a hot water heater out the side of the house? ›

The exhaust gases 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.

How do you install a water heater vent? ›

Hot Water Heater Venting, How To Vent a Gas Water Heater - YouTube

How far off the floor does a tankless water heater need to be? ›

How high should my gas water heater be off the ground? Your gas water heater should be 18 inches off of the ground, as per the National Fuel Gas Code. This is the standard for water heater installation requirements.

How far must a vent pipe be from a window? ›

Each vent must be at least 10 feet from an openable window, door, opening, air intake, or vent shaft and at least 3 feet above a lot.

How far does a tankless water heater need to be from a gas meter? ›

Tankless Water Heaters

Note: PG&E requires a minimum horizontal clearance of 36” between the gas meter and a tankless water heater when located on the same wall.

Is it OK to put a tankless water heater in the attic? ›

Simply put, as long as there is enough combustion air provided, tankless water heaters can be installed in any area of your home, from a utility room to a garage to, yes, even an old, dusty attic.

What is a concentric venting system? ›

The Concentric Vent allows both the intake for combustion air and the exhaust vent to pass through a standard roof or sidewall. This is an alternative to the standard two pipe intake/vent shown in the basic furnace installation instructions.

How does a concentric vent kit work? ›

Concentric Vent Kits - YouTube

Can a water heater and furnace share the same vent? ›

Vent connectors serving equipment vented by Natural draft (typical water heater) Shall Not Be Connected Into Any Portion of Mechanical-draft systems (80% and higher efficiency gas furnaces). This Means: With Any New Furnace Installation — A Gas Water Heater Must Then Be Separately Vented.

Can high efficiency furnace and tankless water heater share vent? ›

When installing a High-Efficiency Furnace, the existing shared vent will not work for only the water heater because the vent is too large for the water heater's exhaust to to warm the pipe enough so it rises safely out of the home. The old vent pipe is too large because it served both the furnace and water heater.

Do gas tankless water heaters have to be vented? ›

Indoor gas tankless water heaters need to be vented. All indoor models have an exhaust vent. Indoor models also need a fresh air intake either from a direct vent or a power vent.

What does a tankless water heater vent look like? ›

TANKLESS - Direct vent exhaust requirements - YouTube

How far does a tankless water heater vent need to be from a window? ›

Indoor Installations

A tankless water heater requires a 4-foot clearance from the side or below a door or window that opens, unless the unit is directly vented to the outside, says Ernie Graves. If the water heater is installed above the door or window, it needs 12 inches of clearance.

Is it normal to smell gas from a tankless water heater? ›

If you smell gas from a tankless water heater, it means there is a leak somewhere, which you need to get fixed out immediately. A tankless water heater will give out gas-only when there is a gas leak or incomplete combustion. Of course, a gas leak is hazardous, so it isn't something you should overlook.

How far can you vent a Rinnai tankless water heater? ›

Vent lengths up to 100' with seven TWH units; 41' with 12 TWH units using 6" diameter venting. There are easy push fit joints—no cement or glue required.


1. Installing a gas vent for a tankless water heater
(Living a Sustainable Dream)
2. Tankless - What to know before you buy
(Matt Risinger)
3. Best Tankless Water Heaters Reviews (2022 Buyers Guide) ✅
4. DEBUNKING Tankless water heater LIES!
(Matt Risinger)
5. Top 5 Best Electric Tankless Water Heater 2022? Buying Guide
(Cool_Tech plus)
6. Tankless Water Heater Install | Existing Home
(Marshall Remodel | MR Post Frame)
Top Articles
Latest Posts
Article information

Author: Gov. Deandrea McKenzie

Last Updated: 02/06/2023

Views: 6545

Rating: 4.6 / 5 (66 voted)

Reviews: 81% of readers found this page helpful

Author information

Name: Gov. Deandrea McKenzie

Birthday: 2001-01-17

Address: Suite 769 2454 Marsha Coves, Debbieton, MS 95002

Phone: +813077629322

Job: Real-Estate Executive

Hobby: Archery, Metal detecting, Kitesurfing, Genealogy, Kitesurfing, Calligraphy, Roller skating

Introduction: My name is Gov. Deandrea McKenzie, I am a spotless, clean, glamorous, sparkling, adventurous, nice, brainy person who loves writing and wants to share my knowledge and understanding with you.