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What are the Likely Causes and Dangers of Sewer Gas Smell in House?

Sewer Gas Smell in House
A sewer gas smell may seem just that- a harmless foul smell; but it is, in reality, quite dangerous and requires immediate attention. What does this smell signify and how is one to treat the same is what we shall be focusing on in the article below.
Rujuta Borkar
Last Updated: Jan 24, 2018

If you've ever had a sewer gas smell in your house and decided to ignore it, it is probably because you did not know the danger that it spells. It is something that should never be ignored and rather be treated with immediate effect. The how and why of the matter is what we shall be discussing now.

Dangers of Sewer Gas Smell
Repulsive Odor
Repulsive Odor

The most basic effect of sewer gas? The smell. The disgusting smell of the sewer waste can make your entire home smell like a toilet bowl. And that is certainly not how we want to live.

Methane Gas (CH4)

Adding to the discomfort of the smell, there is also the danger of poisonous gas. There are traces of methane gas that are found in the sewer smell. Methane gas is very dangerous because it can cause an explosion. Other than that, it can cause fatal asphyxiation (deprivation of oxygen). The sewer content might also have traces of hydrogen sulfide gas (H2S) which can further cause health damages.

Bacterial Infection
Bacterial Infection

Sewer gas smell in the house can also cause bacterial infections which directly affect the sinus. The gas may also lead to mold spores, which in turn will cause problems like asthma, allergies, rashes, and skin irritation.

Causes of Sewer Gas Smell
Low Water Level
Low water level

Sometimes, the water level of the bowl drops, eliminating the barrier that is keeping the gases in the bowl, pushing them to the surface instead. It therefore, allows the gas smell into the house. It is important to maintain the water level and prevent it from drying. Make sure that the flush is flushed at least once every three weeks if no one is using the toilet and more importantly, keep the toilet bowl covered.


There is an extensive network of pipes that goes into the elimination of waste matter and in maintaining the sanitation of the toilet. There might be leaks in the pipes which can cause the smell of sewer gas into the house. It is, therefore, necessary to check for leaks in the fuel gas line, toilet pipes, and appliances. Check for these from time to time to prevent any further danger and get them replaced whenever necessary.

Clogged Pipes
Clogged Pipes

Sometimes, the vent pipe (which is found on the roof or above the house) will get clogged due to debris. This will prevent the gas from being trapped in, letting it out. Without ventilation, the gas will escape into the house. To prevent or get rid of the smell, make sure to have a window screening fitted over all the vent pipes and a clamp to hold it in place. This will keep the pipe free of the debris.

Drain Capping
Drain capping

Redundant drains need to be capped (sealed off) so that the gas cannot escape. Materials like tape provide a temporary solution. Over time, the tape will dry off and lead to the gas escaping through the drain pipes. If certain drains are not in use, they should be properly capped, using the appropriate material so that it does not lead to further damage and a high replacement cost.

Professional Help
Professional help

In spite of these basic steps of checking for and trying to eliminate the gas smell in house, if the problem still persists, then you will need to bring a plumber into the picture. A plumber will have specialized equipment which will help to determine whether there is a leak in any of the pipes.

Plumbers usually use a smoke generator to determine the cause of the gas smell. The pipes and vents are sealed off and the pipes are then filled with white smoke which travels the entire area of the pipes. Thus, when there is even a small leak, it can be easily traced and the repairing done. Other than that, certain other technologies like electronic hand held sewer gas detectors are also used.

Now that you know what can cause the sewer gas smell in house and how to detect it, I hope you will not be forced to suffer further discomfort and danger. This is one task, you should not put off till later.

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