Is Gas Water Heater Exhaust Dangerous? Getting Your Facts Straight

Are you among those who often wonder, “Is gas water heater exhaust dangerous?” Most people today have water heaters for their comfort, and most of them are running on gas.

However, the exhaust gas must be directed and vented correctly so it won’t be trapped inside the house and cause health hazards. In most cases, the gas can be dangerous and risky. When prolonged for a long time, it may cause serious health problems. So, what should you know about this issue?

Is Gas Water Heater Exhaust Dangerous?

Worried about gas water heater exhaust being dangerous? It’s all about the vent pipe. This pipe carries away the hot gases that the heater makes, keeping the air in your home safe. It’s super important to set it up to stop bad gases, like carbon monoxide, from entering your house.

Read also: Is Hot Water Heater Knocking Dangerous?

Carbon monoxide is a sneaky gas you can’t see or smell, so having a detector near your water heater is smart. It’ll let you know if there’s a problem. Also, ensuring enough fresh air around your water heater helps it work better and keeps dangerous gases from returning inside.

Keeping the area around your water heater well-ventilated is key. This means the heater gets enough air to work and keeps you safe from those harmful gases. If you’re unsure, it’s best to get a pro to check things out and ensure your vent pipe is doing its job.

is gas water heater exhaust dangerous

How Dangerous Is Water Heater Backdraft?

Many homeowners often don’t understand backdraft and the possibility that it may happen. If you are wondering if gas water heater exhaust is dangerous, then you should know that it’s deeply related to backdraft.

The (atmospheric) venting water heater has this unique design where the hot (exhaust) gas should naturally rise and come out of the chimney. If the vent is installed correctly, you won’t have to worry about the exhaust gas problem. However, if the installation is incorrect, the exhaust gas won’t be able to come out of the chimney. Instead, it would go back down to the house, and it would cause a backdraft.

Read also: Gas Hot Water Heater Venting Requirements

A backdraft is a situation where the (toxic) combustion gasses can be dangerous to the family members because they aren’t vented properly. This situation is dangerous and shouldn’t be taken lightly.

The combustion gasses should rise up via the chimney and then be released outside. But instead of it, the gas is entering the house back and endangering the people. Backdraft is a common issue with atmospheric gas water heaters.

How to Tell if Your Water Heater Is Venting Properly

It’s good that there are ways to check whether your heater has a backdraft issue. There are some easy ways to do the checking:

  • You can place a mirror (just a small one) close to the draft hood. If there is fog on the mirror, then it’s proof that moist air is present.
  • Cup the hands around the existing draft hood. It’s a vertical pipe with a cone shape located at the top area of the heater. If you feel moist and warm air, then you have a backdraft.
  • The water heater has a plastic cap on top of it (where the vent is located). If the plastic cap is deformed or melted, you have a backdraft.
  • Check the draft hood for the presence of soot or dark residue
  • You should also check the heater’s top area for corrosive stains. If you see them or spot moisture on the top side of the tank, it can be a solid sign of back-drafting.

The Logical Solution

If back-drafting truly happens, then don’t freak out. Calmly improve the ventilation by running an exhaust fan nearby or opening the window. Then, contact a professional and skilled HVAC technician to check on your heater and perform a repair. He/she may have to replace any missing vent cap, install a (power) vent or correct the setup of the heater’s ventilation.


In the end, if you ever suspect your water heater is somewhat problematic, you must have it checked immediately. You won’t have to worry about is gas water heater exhaust is dangerous. You have taken care of your heater correctly.

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Heater Technician is a skilled author and water heater expert with years of experience in the field. He has authored several articles and books on various aspects of water heater installation, maintenance, and repair.