Backdrafting Water Heaters

In today’s highly efficient homes, backdrafting water heaters have become an increasingly common issue, especially in newer residences in areas like western Shawnee and South JOCO. But what exactly is backdrafting, why does it happen, and most importantly, how can you prevent it in your home? Let’s explore.

What is Backdrafting?

Backdrafting occurs when exhaust gases from your water heater, which should be safely vented outside, are instead drawn back into your home. This issue is largely due to imbalances in the HVAC system, resulting in negative pressure in your basement.

Most gas water heaters operate on atmospheric venting, meaning they rely on the principle that heat rises to vent exhaust gases. Without a fan to push these gases outside, negative pressure can cause the exhaust to backdraft into your home, risking your health and safety.

Various Examples of Backdrafting Scenarios

Why is Backdrafting More Common in Summer?

Interestingly, backdrafting is more likely to occur in the summer months. That’s when we typically redirect conditioned air to the upper parts of the house, often leaving the basement out of balance. If most intake air is pulled from the basement while the conditioned air is directed upwards, a negative pressure environment can occur. This can lead to backdrafting.

How to Spot Signs of Backdrafting

Hot water heater

One indicator of backdrafting is the presence of a dust line on the door stop leading down to the basement. Another sign is if your basement door tends to pull shut when the air conditioning is activated, both are symptoms of the negative pressure that leads to backdrafting.

Furthermore, inspect your water heater for signs of backdrafting. Look for a plastic ring around the inlet and outlet nipple of the water heater. If this ring appears melted, it’s an indication that the drafting of the water heater may not be functioning properly.

How to Prevent Backdrafting

Preventing backdrafting involves some straightforward steps. First, ensure there are no significant leaks or gaps in your cold air return ductwork. If your basement is unfinished, inspect the return air ductwork as leaks can sometimes be overlooked during construction.

Next, consider adding combustion passage louvers from the basement to the mechanical room and from the basement to the first floor. This adjustment can help regulate airflow and prevent negative pressure from forming. Also, keeping a supply air register open in the basement or mechanical room can help balance the system.

Lastly, ensure that your venting is properly sized and configured, as many homes in Johnson County don’t meet Fuel Gas Code requirements. Proper vent configuration can significantly decrease the chances of backdrafting.


Backdrafting is a serious issue that can pose a risk to the health and safety of your home’s inhabitants. By understanding the causes and signs of backdrafting, and implementing preventative measures, you can protect your home. If you’re unsure about your water heater’s condition or want professional help to prevent backdrafting, reach out to your local Kansas City Water Heater experts.

Remember, if you’re unsure or uncomfortable performing any of these checks or adjustments, it’s always best to consult with a professional. Safety should be your paramount concern when dealing with potential backdrafting issues.