Nicolette Forbes

By: Nicolette Forbes on July 15th, 2022

Print/Save as PDF

Can I Use My Existing Venting for My Tankless Water Heater?

Tankless Water Heaters

Are you interested in getting a new tankless water heater but are unsure if you can use your current venting? Venting is commonly overlooked by most homeowners because many are overwhelmed with the other adjustments such as gas lines, space, and size. But that stops now. 

In this article, we will discuss: 

  • The importance of venting for tankless water heaters
  • Different kinds of venting for tankless water heaters
  • Venting requirements
  • Answering the question: “Can you use existing venting for your new tankless water heater?”

Monkey Wrench Plumbing has been in business for over 15 years, and we have helped thousands of clients, especially with their tankless water heater needs or questions. We are passionate about what we do, and by the end of this, you will have a better understanding of whether or not it is possible to use existing venting systems for your new tankless. 


Is Venting for Tankless Water Heaters Important?

When purchasing a tankless water heater, it is important to know that, along with gas and electric models, there are also interior and exterior models available. The main difference between interior and exterior tankless water heaters is how they are vented. But is venting that important for a tankless water heater's overall performance?

In short: YES! Making sure you have the right ventilation is key when installing a gas-powered tankless water heater. Improper ventilation can lead to some serious consequences, including: 

  • Early breakdowns/failures of the tankless water heater
  • A shorter lifespan for your tankless water heater due to condensate (water) being allowed to enter the tankless water heater
  • Carbon monoxide poisoning 

You definitely don't want to take shortcuts or cut corners here. We recommend that you follow the manufacturer's instructions to ensure that your tankless water heater is properly vented.

We also mentioned that proper ventilation is important for gas-powered tankless water heaters, but what about electric tankless water heaters? Unlike gas or propane tankless water heaters, electric tankless water heaters do not need venting because they use electric burners to heat water rapidly. Since no natural or propane gas is used, no venting is needed.


Tankless Water Heater Vent Types

Like tankless water heaters, there are also different types of vents for tankless water heaters. The best kind of vent for your home depends on several things, including: 

  • The tankless water heater’s positioning
  • Its size
  • How much space is needed as different types of tankless water heaters require different vents

The different types of vents include:


Power Vent

Power vents use indoor air to create the heat for your water and work by moving that same air outside. Because of this, power vents only need one exhaust vent. Additionally, power vents require a larger space where sufficient air is available.


Direct Vent

Direct vents have two vents: one of which functions for intake by pulling air into the home from the outside and exhausting or removing air. They can be installed in smaller areas, like closets, with less excess air in the immediate environment. Because of their smaller size, direct vents make an excellent choice if limited space is a concern.

Different types of water heater venting 

Concentric Vent

Concentric vents are two vents in one: a single vent that has both intake and exhaust direct vents. This means that tankless water heaters require less surface space when being installed. Concentric vents are not hot to touch like direct vents. Additionally, concentric vents are far safer, as the exhaust air is contained, preventing the leaking of harmful gasses into the home.

The parts of water heater venting

Overall, having an efficient venting system is crucial for ensuring the safety and functionality of your tankless water heater.


Venting Requirements

Tankless water heater venting must be done correctly to ensure the safe and efficient operation of the unit. Here are a few things your installer should consider for effective tankless water heater venting:

  • Vent to the outside
    • Having the venting go outside will help avoid harmful gasses like carbon monoxide entering your home. 

  • No shared venting
    • The tankless water heater cannot share vent piping with any other appliance, and it cannot use a chimney for venting.

  • Short vent run
    • The vent should be as short as possible to make sure the harmful gasses are removed from the home. Since the stainless steel vent pipe is much more expensive than the gas supply and water supply piping, it makes sense to move the tankless heater closer to where the vent will leave the house.


Can You Use the Existing Vent for the Tankless Water Heater?

It is not recommended that you use the existing vent pipe from an old gas tank water heater. The existing vent for tankless water heaters may not be compatible because most are galvanized vent piping and will rust quickly. It is similar (but not the same) to getting a new car but putting the old tires on the new car. You wouldn’t dream of doing that, right? Special stainless steel pipes should be used for venting unless plastic materials such as PVC are suitable based on the vent manufacturer’s guidelines.

Read this article here to learn more about ways tankless water heaters are installed incorrectly as we share a few points regarding venting and gas lines. 


Closing Out Venting For Tankless Water Heaters

Having the proper venting for your tankless water heater is important for several reasons but you should not use venting from an old gas tankless water heater on a new tankless water heater. Doing so can cause many problems, including early breakdowns with your tankless, shortened lifespan of your tankless, and carbon monoxide poisoning. 

However, if you have an electric tankless water heater, you do not have to worry about venting. This is because they use electric burners to heat water instead of natural gas or propane, eliminating the need for venting.

Want to learn more about what other parts of your home may need adjusting due to a new tankless water heater? Check out the articles below to help you decide whether or not you need to upgrade your gas line to have a tankless and if you need a water softener for your tankless.

Do I need to upgrade my gas line with a tankless water heater?

Do I need to install a water softener for my tankless water heater?

When it comes to tankless water heaters, Monkey Wrench Plumbing wants to set you and your home up for success. If you live in the Los Angeles area and have any other questions regarding tankless water heaters you can call us at 310-853-8690, and one of our call center representatives would be happy to help you.