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Water Heater Venting 101

Water Heater Venting

What is Water Heater Venting? Why Do You Need Water Heater Venting? Types of Water Heater Venting

Gas water heaters heat water by burning natural gas or propane. This process releases a lot of gases which need to be vented for safety reasons. You might have a direct vent water heater, or a power vent water heater based on your venting configuration. In this article, we will look at a few things that you should know about when it comes to venting a water heater. Let’s begin with the foundations.

Table of Contents

What is Water Heater Venting?

Gas water heaters burn a fuel to generate the energy needed to heat water. This process of fuel-burning (known as combustion) releases a lot of byproducts in the form of exhaust gases and moisture. The removal of exhaust gases released during the combustion process of gas-powered water heating is called venting.

Why do water heaters need to be vented? What happens if I do not vent a gas-powered water heater?

A gas-powered water heater should not be operated unless it is properly vented. In the United States, it is required by law for gas-powered water heaters to be vented.

  • Firstly, water heating venting ensures safety. One of the gases released during combustion is carbon monoxide. Being highly poisonous, carbon monoxide needs to be vented properly to avoid serious health concerns. 
  • Secondly, improper venting can cause your water heater to backfire/overheat. This can be unsafe and damage your water heater beyond repair.
  • Thirdly, improper venting can void your water heater’s warranty. Many manufacturers provide a warranty for their water heaters only if they have been installed with proper venting. Hence, not venting your water heater is also crucial for monetary reasons.
  • Lastly, improper venting can cause your water heater to function improperly. The process of combustion requires an adequate supply of oxygen. If a water heater is not vented properly, the buildup of exhaust gases can reduce the amount of oxygen present in the atmosphere.

What is backdrafting?

It is paramount for venting to be carried out properly. Improper venting of a water heater can result in something called backdrafting. Backdrafting occurs when an improperly vented water heater’s exhaust gases end up re-entering the home/property accidentally.

Types of Water Heater Venting

There are various ways in which a water heater can be successfully vented. Let’s take a look at some of the most common means. 

1. Atmospheric Venting

Atmospheric Venting is the process of removing exhaust gases from a water heater through a vertical duct that expels them outwards through the roof (likely via the common exhaust system/chimney).

Atmospheric Venting is the most common form of water heater venting. With atmospheric venting, a vertical duct typically carries the exhaust gases away from the water heater upwards. The exhaust gases rise and travel out of the property via the duct and through the roof (likely via a chimney). In many cases, the vertical duct is tied into the property’s common vent.

Atmospheric venting works because hot gases naturally move upwards. However, atmospheric venting is highly susceptible to backdrafting.

2. Direct Venting

Direct Venting is the process of removing exhaust gases from a water heater by installing an inlet vent pipe and an outlet vent pipe (through the wall) in order to create an airflow.

Direct venting is another form of water heater venting. Direct vent water heaters employ a process similar to atmospheric venting. However, direct venting can be carried out with horizontal exhaust pipes rather than vertical exhaust pipes. Hence, when it comes to direct venting, the water heater’s exhaust gases travel sideways rather than upwards.

This form of venting is made possible by having separate inlet and outlet vents to create a flow. Hence, one vent pipe brings air from the outside to the water heater, through the wall. Another vent pipe carries the exhaust gases away from the water heater to the outside, through the wall. By having an inlet and an outlet vent pipe, a natural flow is created, allowing the passage of exhaust gases.

3. Power Venting

Power Venting is the process of removing exhaust gases from a water heater by installing an inlet vent pipe and an outlet vent pipe as well as an electric fan to create better airflow.

Power Venting is a form of assisted water heater venting. Power vent water heaters have horizontal or vertical exhaust pipes assisted by an electric fan. The electric fan helps propel air to create the flow required for venting. Secondly, they also cool the air, allowing power vent water heaters to make use of PVC pipes for venting instead of metal ones.

Due to a fan, power vent water heaters are typically more effective at expelling exhaust gases quickly. However, the fan also necessitates the availability of an electric outlet near the water heater.

Tankless Water Heater Venting | Do Tankless Water Heaters Need to be Vented?

Although tankless water heaters do not store and heat water constantly, they still need to be vented. Tankless water heaters also undergo the process of combustion and need to dispel exhaust gases. Hence, for all the reasons mentioned above, it is necessary to vent a gas-powered tankless water heater properly.

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