House Smells Like Gas But No Leak? (Here's Why!)

Stacy Randall
by Stacy Randall

Nothing is quite as unnerving as the odor of natural gas in your home. Everyone is aware of the danger posed by natural gas leaks. If you can’t locate the source of the odor, the level of anxiety grows quickly. If you smell gas in your home and can’t find a leak, there are several possible causes.

Sulfur or hydrogen sulfide is the usual cause of natural gas smells in a home when there is no leak. Hydrogen sulfide is produced by bacteria in sewers and drains. Water heaters can produce the same smells if they are not used and drained regularly. These sulfur odors aren’t hazardous but should not be ignored.

In any case, a smell that resembles natural gas should get your attention quickly. Everyone is familiar with the dangers a natural gas leak can pose. Even if it is not natural gas, the odor usually indicates some other kind of problem. The cause of the odor may be almost as dangerous as natural gas to your home and your health.

What Can Produce a Smell Like Natural Gas in Your Home?

Natural gas does have a very distinct and pungent odor. The smell is often compared to rotten eggs. Most people don’t realize that natural gas doesn’t have an odor. Gas utility companies add the odor to the natural gas to make it easier to recognize a leak.

According to the Public Utilities Regulatory Authority, gas companies as mercaptan to natural gas to produce the rotten egg smell. Mercaptan is a harmless chemical called an odorizer used extensively to provide a distinctive smell to several odorless gases. The smell of rotten eggs can be created in several different ways that may find their way into your home.

Sewer Gas in your Home

One of the most common causes of that rotten egg smell in a home with no gas leak is sewer gas that has found its way back up the sewer lines. The bacteria associated with a lack of oxygen and decaying organic matter smell like natural gas.

Often, the path from the sewer for this gas into your home is back through the sewer pipes. A little-used bathroom may have P-traps that have dried out and leave an open pipe. Clogged vent pipes can also cause sewer gas to be vented back into your home.

Is Sewer Gas Dangerous?

The International Association of Certified Home Inspectors notes several dangers accompanying sewer gas in your home.

These dangers include:

  • The compound that causes the rotten egg smell of sewer gas is hydrogen sulfide. In larger concentrations, hydrogen sulfide can be toxic or cause other severe physical problems.
  • Sewer gases can displace oxygen in your home and pose a potential asphyxiation hazard. Sewer gases tend to be heavier than air and accumulate in the lowest portions of your home. Basements can become extremely hazardous if a sewer gas problem allows the basement area to fill with hydrogen sulfide.
  • Often, methane accompanies the hydrogen sulfide in the sewer gas. At the right concentrations, methane can be a fire or explosion hazard in your home.

If you have a rotten egg smell in your home and are sure that there are no gas leaks, you should suspect a sewer gas problem. Your drains and sewer system should be checked completely by a licensed plumber to ensure no damage to the system, clogs in the vents, or other problems.

Check Your Water Heater

A water heater that isn’t used regularly may be invaded by bacteria. The bacteria can produce hydrogen sulfide and the recognizable odor of rotten eggs when the hot water is turned on at a faucet. The University of Georgia Extension Service offers some insight and advice about hot water that smells like rotten eggs.

The University of Georgia Extension service advises that hot water heaters that are seldom used or have the thermostat set too low are prone to developing this problem. This situation occurs in larger homes where most of the family has left, and one or more bathrooms get little use. Bacteria begin to grow in the unused water heater, resulting in the smell of rotten eggs.

The key to solving this problem is to occasionally run hot water in some of the fixtures of these seldom-used parts of your home to flush the water heater tank. Keep the thermostat set high enough that the temperature of the water impedes the growth of bacteria.

A magnesium anode can impart this odor to the water in some instances. Have your plumber replace the magnesium heating element with an aluminum anode to solve the problem.

Is the Water OK to Use if it Smells Like Rotten Eggs?

In general, the bacteria in a water heater that produces obnoxious odors is not a health risk. However, drinking or cooking with this water is generally not a good idea. The odor and taste alone make it almost impossible for anyone to drink or cook with this water.

Your Well May Be the Source of the Odor

Rural homes that depend on their domestic water from a well may experience rotten egg smells in the water. Occasionally, bacteria growth in the well may create these odors. If the water from your domestic well starts to smell like rotten eggs, you should take immediate action. A contaminated water well may contain other bacteria that pose health risks. Have your water well inspected and tested by a certified well technician.

If your well is contaminated, the well should be thoroughly flushed and cleaned. This will probably include disinfecting the well, well casing, and pump. This process should be performed by a qualified technician, and water testing is done by a certified lab after the cleaning and disinfecting are performed.

Check for an Improperly Operating Septic System

If you live in a rural area and depend on domestic water well, you probably also have a tank and drain field septic system. If the septic system is damaged or malfunctioning, it may be leaching sewage into or around your water well. This is an extremely dangerous situation that should be corrected immediately.

Contact a licensed plumber or septic system technician to inspect your septic system. Do not use the water from your well if you suspect your septic system allows sewage back into your water well.

It May Be Natural Gas you Smell

You may be absolutely certain that there is no natural gas leak in your home. This doesn’t necessarily mean that natural gas is not getting into your home from another source. Natural gas is a slippery character and will travel a long way along the most circuitous routes at times. Just eliminating leaks in your home doesn’t mean you aren’t being plagued by leaks elsewhere.

You May Have a Leak Outside your Home

Every home with natural gas service has a main supply line to deliver gas. Typically, this supply line is connected to the gas meter somewhere outside your house and runs underground to your home. The typical installation is to raise the underground gas line above grade outside your home with a riser tube that protects the gas line from damage.

The other function of this riser tube around the gas line is to allow any leaking natural as that follows the main gas line to exhaust into the air and not into your home. Unfortunately, some homes are not protected by this simple installation. A leak in the gas main can easily follow the underground gas pipe into your home. Even if your home gas piping is secure and leak-free, you can experience natural gas inside your home if this condition exists.

How Will I Know if I Have a Gas Leak Outside?

ENSTAR, a large natural gas company, lists several signs that indicate a natural gas leak outside your home. A bit of detective work on your part may help determine if there is a problem with the main gas line feeding your home.

  • Look for dead or discolored vegetation in your landscape. Lawn grass is especially sensitive to natural gas. Yellow rings or circles in an otherwise green lawn may indicate where natural gas is escaping from underground.
  • If you notice dust puffing or spewing from cracks in the soil or holes in the ground, you should suspect a natural gas leak. If the area is damp or wet, you may notice bubbling or gurgling from the ground.
  • Hissing sounds can sometimes be heard near the natural gas leak.

ENSTAR recommends that you contact your gas utility immediately if you notice any of these telltale signs. A large natural gas leak is certainly nothing to take lightly. Even a small leak can pose a danger to your home if not repaired promptly.

Whose Responsibility is a Leak in the Main Gas Line

In most cases, the leak’s location determines who’s responsible for repairing the gas line. In general, if the leak is on your side of the gas meter, you are responsible for maintaining and repairing the gas line.

Suppose the leak is in the gas meter or in the piping on the side opposite your home. In that case, the gas utility company is responsible for maintaining and repairing this equipment.

Is the Gas Smell Migrating from an Adjacent Apartment?

It is not uncommon for the smell of natural gas to come from somewhere else in the building in multiple occupancy buildings. A neighboring apartment may have a gas leak, or the piping system that serves the building may leak.

If you live in a multiple occupancy apartment building and smell gas in your apartment, you should take immediate action. You may not have a leak, but a leak elsewhere in the building can have catastrophic results if not repaired.

Any suspected gas leak should be promptly reported to the fire department. Follow the instructions that the fire personnel give you. It may be necessary to evacuate the building if the source of the leak is not found promptly.

Other Sources of Rotten Egg Smells in Apartment Buildings

Many large apartment complexes, especially high-rise apartment buildings, feature trash or garbage chutes. If the garbage chute becomes overwhelmed or suffers a blockage, the decaying garbage can produce the rotten egg smells associated with a gas leak. A visual inspection of the garbage chute often reveals the source of these odors.

More than likely, you aren’t the first to notice this situation. However, you should immediately report the situation to the building superintendent for remediation. Decaying garbage is a health hazard and an obnoxious odor-producing situation.

Atmospheric Odors May Be to Blame

At times your local gas utility company may release natural gas into the air during maintenance or repair projects. This can cause the rotten egg odor to spread over a wide geographic area in short order.

Most states require that natural gas utilities promptly report any natural gas emissions into the open air. If you notice the smell of natural gas inside your home and outside as well, more than likely, the gas company has vented gas for some reason.

A quick phone call to the customer service number for your local gas utility company can quickly confirm the situation. If the gas company has been repairing the gas lines and suffered a leak, the customer service office an give you the details.

If You Smell Gas and Don’t Have a Leak

The smell of rotten eggs in your home doesn’t necessarily mean you have a gas leak and a problem. However, the other causes of that rotten egg smell in your home other than natural gas can also be a problem. Not only can it be irritation, but it may also have health ramifications for you and your family. The odor may also be a symptom of bigger problems that need to be addressed.

Stacy Randall
Stacy Randall

Stacy Randall is a wife, mother, and freelance writer from NOLA that has always had a love for DIY projects, home organization, and making spaces beautiful. Together with her husband, she has been spending the last several years lovingly renovating her grandparent's former home, making it their own and learning a lot about life along the way.

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