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How to Vent a Tankless Water Heater in 4 Easy Steps

Fact checked by Stephen Conklin

how to vent a tankless water heater

Mastering how to vent a tankless water heater is one of the skills that any modern homeowner should learn. Not only does it show compliance with the local venting code, but it also underscores the value placed on safety.

Tankless gas water heater venting might seem more complicated than a conventional storage-type water heater. However, we will share two ways to evacuate tankless water heater exhaust gases from your house safely and efficiently.

Let us start.

Table of Contents

Ways to Vent a Tankless Water Heater

What to prepare

  • Tankless water heater vent kit – power or direct
  • Water heater-specific installation guide (i.e., Rinnai tankless water heater venting installation)
  • Vent pipes
    • Stainless steel and metal are the best materials for vent pipes, as they can withstand high temperatures. In addition, they’re better at handling corrosive gases.
    • Vent pipes for systems with a condensing unit, however, can use PVC to vent a tankless water heater.
  • Duct tape (or foil tape)
  • Caulk
  • Power drill and hole saw (or a hammer and chisel)

Step 1. Decide how to vent your tankless water heater.


The first step in addressing your tankless water heater’s venting requirements is determining the vent type you will use. Experts recommend either a power or a direct vent system. It’s best that you review the venting diagram for each type to see which one would best fit your home.

  • Please note that a power vent requires an electrical outlet to connect the system’s blower component. This device pulls hot air and combustion byproducts from the tankless water heater and pushes them outside.

Direct venting systems do not have such elements, so a nearby electrical outlet is unnecessary.

  • Power venting ducts can run horizontally from the water heater, making them ideal for venting through the wall.

Direct systems, meanwhile, require a sloping or vertical orientation. Hence, direct vents could be an excellent option for venting through roof.

Step 2. Review local venting regulations and manufacturer recommendations.


The ANSI Z223.1/NFPA.54 National Fuel Gas Code specifies the different tankless water heater PVC venting regulations that homeowners should know. That said, note that these guidelines are separate from local laws. Hence, you might want to check your area’s local regulations.

  • Look for the minimum venting distance between the tankless water heater and surrounding objects.

Usually, for single-wall pipe, a 6-inch clearance is required, whereas draft hood connections call for up to 12 inches of the vertical vent.

  • Know the local guideline for venting a tankless water heater with furnace In California, for example, such systems will be outlawed in 2030, so you may want to avoid these entirely.
  • Check the water heater manufacturer’s installation manual for other details. For example, a Navien tankless water heater might have a different installation requirement from a Rinnai or Rheem tankless water heater.

Step 3. Prepare the venting structure.


This step can be an issue if you install a vent pipe for tankless water heater for the first time. Hence, there are two key points you should never forget:

  • Please do not use existing vent systems to connect the tankless water heater because the two might be incompatible.
  • Experts also don’t recommend sharing the tankless water heater with a common vent pipe through chimney due to their differences in venting requirements and back-drafting issues.

With the two tips above in mind, here are the steps to prepare the structure for venting pipes:

  • Use a power drill and hole saw (or a hammer and chisel) to create a hole in the sidewall. The opening must be large enough to accommodate the vent pipe’s diameter.
  • For a non-condensing unit, make sure the sidewall opening is slightly lower than the tankless water heater’s vent, with a ¼-inch slope per foot of vent pipe lengt

A condensing tankless water heater, meanwhile, must have a sidewall opening higher than the water heater’s vent (1/4-inch slope per foot).

  • Please create two holes (at least a foot apart) for the direct venting systems – one for the exhaust vent and another for the combustion air intake.

Step 4. Install the vent pipes.


Installing tankless water heater vent pipes in garage, basement, or other spaces is easy if you follow the manufacturer’s installation instructions. After all, you only need to link the vent ducts to the system’s termination.

  • Secure the water heater venting system’s terminal section (the one that ends outside the home). Ensure it has adequate protection against the elements by installing a vent cap, weather collar, and draft hood.
  • Connect and fasten a vent duct from the tankless water heater’s top.
  • Link a 90-degree elbow to the vertical vent’s topmost section and use PVC to vent a tankless water heater towards the sidewall.
  • Add another right-angle elbow connector at the ductwork’s end outside the house.
  • Use either duct tape or foil tape to secure the venting pipe connections. Then, seal any holes in the fan housing with caulk.

Fix It Scotty prepared this video to help you ace the art of venting a tankless water heater.

The Importance of Venting Tankless Water Heaters

We cannot help but overemphasize the significance of venting tankless water heaters. Like conventional storage tank-type heaters, these units rely on propane, natural gas, or other combustible fuels to produce heat and raise the water temperature.

Unfortunately, combustion creates many byproducts, including carbon monoxide, carbon dioxide, hydrocarbons, sulfur dioxide, nitrogen dioxide, particulates, and more.

Tens of thousands of Americans seek emergency medical services for accidental carbon monoxide poisoning. Unfortunately, around 400 folks lose their lives after inhaling this toxic combustion byproduct each year.

Although a tankless water heater is small compared to a storage tank type, it can still create combustion byproducts that undermine a family’s health and safety.

Preventing these combustion byproducts from harming your family is easy if you properly vent your tankless water heater. Venting systems draw toxic fumes from the water heater and move them outdoors to disperse.

If you dislike the tedious process of venting, you might want to ditch gas-powered units for electric versions. Electric tankless water heater venting is unnecessary because the heating mechanism doesn’t produce combustion byproducts.

Things to Consider about Venting Tankless Water Heaters

Venting tankless water heaters can be challenging to the uninitiated. Unsurprisingly, many homeowners hire professionals to install the system and eliminate the hassle of considering various factors.

However, you can still think about the following if you want to vent the system yourself.

1. Indoor vs. outdoor units


Outdoor water heaters don’t require venting because the combustion byproducts dissipate readily into the atmosphere. However, you might want to check the product’s weather protection to ensure it can withstand harsh climates.

Meanwhile, indoor versions will always need venting. Otherwise, combustion byproducts can accumulate indoors and harm the house’s occupants.

2. Power vs. direct venting systems


Direct systems require two holes for the exhaust vent and the combustion air intake. Hence, if you don’t want to tax yourself, a power venting setup might be a better option.

Unfortunately, power venting requires a larger room to draw indoor air for combustion. Meanwhile, direct systems will work fine with only 16 square feet of floor area.

3. Condensing vs. non-condensing water heaters


Condensing water heaters have a 95% energy efficiency rating and a lower-temperature exhaust gas. Hence, you can use polypropylene or PVC vent pipes instead of metal. These materials can lower overall installation costs.

4. Concentric vent design


If you choose direct venting, consider adding a concentric vent to safeguard the system against leaks. This device also makes the vent cooler, allowing you to maintain the system effortlessly.

5. Aesthetics

Consider recess boxes to “hide” the tankless water heater within the walls. Not only do these elements improve the unit’s aesthetics, but they can also save space. You can add decorative terminals and vent pipe covers to make your tankless water heater look more elegant.


Mastering how to vent a tankless water heater is easy if you observe the manufacturer’s step-by-step installation guide. Noting the different venting guidelines and learning various tricks can also help make this endeavor more manageable.

Our four-step process seems simple enough. However, we must reiterate the significance of spending time discerning between a power venting system and a direct venting setup you should pick.

Otherwise, an experienced and licensed professional can address all your concerns without exerting anything.

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