Can You Get Carbon Monoxide Poisoning from a Water Heater?

According to the CDC, at least 430 people die every year in the US from unintentional carbon monoxide poisoning. Fifty thousand people visit the emergency room annually with symptoms of carbon monoxide poisoning.

Why? Read on.

Gas appliances such as furnaces and water heaters are the most common causes of carbon monoxide leaks in homes. Also, any appliance that undergoes combustion of fossil fuels (coal, charcoal, kerosene, and wood), such as an oil furnace, gas stovelawnmowercharcoal grills, fireplaces, etc. can release carbon monoxide in your home if not well ventilated.

Below is everything you need to know about gas water heater carbon monoxide leaks.

Does a Hot Water Heater Put Out Carbon Monoxide?

Unlike electric water heaters, propane or natural gas water heaters produce carbon monoxide. Both tank and tankless water heaters that use gas or propane have an operational mechanism whereby the gas or propane is burnt in the process of combustion to produce heat, carbon monoxide, and moisture.

On the other hand, electric water heaters have heating rods on the heat exchanger that heat the water, and therefore they do not produce carbon monoxide.

vent pipe

Water Heater Venting Basics

Propane and gas water heaters are fitted with a venting system. The venting system constitutes of a flue, also known as a chimney, exhaust pipe, vent pipe, or vent duct, that directs the exhaust gases and moisture produced during combustion outside the house, where it has minimal effects.

There are various venting systems for water heaters, including atmospheric vents, power vents, and direct vents. Although each has a different venting technique, they draw out carbon monoxide fumes and, in some cases, take in combustion air. If there is not enough oxygen for the combustion process, a higher amount of carbon monoxide is produced.

The venting system should be installed properly to prevent back-drafting. Otherwise, it can cause a carbon monoxide leak in your home.

How Do I Know If My Water Heater Is Leaking Carbon Monoxide?

A carbon monoxide leak can often go unnoticed until it causes unintentional carbon monoxide poisoning to the home dwellers. This is because carbon monoxide is an odorless and colorless gas.

Therefore, unless you have a carbon monoxide detector installed, you may never know if it is present in your home. With that said, you may notice some signs of carbon monoxide build-up in your home or depict some symptoms of carbon monoxide poisoning.

Physical Signs of Carbon Monoxide Build Up

If carbon monoxide is beginning to build up in your home, you may notice the following:

  1. Soot or yellowish-brownish stains around the water heater
  2. Lack of upward draft in the flue. To test if the venting system is working properly, set the water heater thermostat on high. Place your finger on one of the open parts of the hood of the venting system. Or, light a matchbox and place the flame near the open parts of the hood. If the venting system is working properly, you should feel a sucking sensation on your finger, or the frame should be drawn inwards.
  3. Inspect the color of the flame. Ideally, it should be blue. A yellow flame might indicate that the combustion exchanger is not receiving enough oxygen, which results in high levels of carbon monoxide.
  4. Stale or stuffy smell in the air. Although carbon monoxide is odorless, it may combine with other exhaust gases to produce a stale smell in the air.

Symptoms of Carbon Monoxide Poisoning

Since carbon monoxide build-up in your home is often unnoticed and can lead to death within a few hours, CO is also known as a silent killer. However, there may be some tell-tale signs of carbon monoxide poisoning.

If you notice that you, other home dwellers, and pets have any of the below symptoms, particularly when you are at home and symptoms ease when you leave the house, investigate the carbon monoxide leak immediately.

  • Headaches or tightness in the forehead
  • Dizziness
  • Confusion or disorientation
  • Weakness
  • Stomach upset
  • Nausea
  • Vomiting

Related Post: No Hot Water In Shower But Sinks Are Fine – Solved

What to Do If You Suspect Carbon Monoxide Leakage in Your Home

If you suspect a carbon monoxide leak in your home, leave the house immediately and stay outdoors. If anyone has symptoms of carbon monoxide poisoning, take them to the nearest ER or call for an ambulance. Contact the fire department and report that you suspect there is a carbon monoxide leak in your home.

What Causes Water Heater Carbon Monoxide Leakage?

The most common causes of a water heater carbon monoxide leak include:

  • Improperly installed venting system
  • Blocked venting system. A venting system can block as a result of birds building a nest in the venting pipe, dead squirrel or squirrel remains, and accumulations of dirt and dust
  • Inadequate oxygen supply to the combustion chamber

How to Prevent Gas Water Heater Carbon Monoxide Leakage

The following are important measures to take to prevent or detect a water heater carbon monoxide leakage:

  • Ensure that the venting system is installed properly. Have it installed by a professional, reputable plumber
  • Install a carbon monoxide detector. The carbon monoxide detector alarm goes off if the levels of carbon monoxide in the room exceed a preset level.
  • Have your water heater inspected at least once every year or as part of routine maintenance by a professional plumber. The plumber will identify early on any malfunctions in the venting systems that could lead to a carbon monoxide leak.
  • Ensure the water heater’s site of installation is well ventilated. This ensures that the combustion chamber receives an adequate amount of oxygen for the combustion process. Also, in case of a leak, the carbon monoxide will find an outlet outdoors.


Generally, water heaters are safe. They operate silently to ensure you have an adequate supply of hot water in your home. However, if the venting system is faulty, it possesses the risk of carbon monoxide leakage, leading to adverse effects on your health or even death.

Therefore, it is important to have your gas or propane water heater installed by a reputable professional to ensure the venting system works properly. Also, install a carbon monoxide detector in your home.

Water Heater Carbon Monoxide FAQs

Is It Safe to Sleep Next to a Water Heater?

It is not recommendable to sleep next to a water heater, whether gas, propane, or electric. This is because any malfunctions such as carbon monoxide lead, water leakage, or overheating can have dire consequences on your health.

With that said, in cases where there is limited space, some local governments allow the installation of water heaters in a bedroom closet. The caveat is that you get a permit, have the water heater installation inspected, and keep the closet doors closed.

Does Opening Windows Clear Carbon Monoxide?

Yes. Opening the windows allows the air to flow in and out. As such, the incoming air dilutes the carbon monoxide, and as it flows out, the carbon monoxides also go out. If the carbon monoxide build-up was too high, then it may take longer to get rid of it by opening the windows.

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