How to Identify and Fix Sewer Gas Smell in Your House

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how to identify fix sewer gas smell in your house

Unpleasant odors in your home can be quite irritating. But if there is a sewer smell in the house, similar to that of rotten eggs or cabbage, you may have a sewer gas leak. Gasses off-put by the sewer are a byproduct of the breakdown of waste. But the pungent smell they create is not just disgusting – these gasses can be dangerous as well.

A high level of sewer gases in a home is considered a fire risk because it’s made up of flammable compounds, such as methane and ammonia. Also, sewer gasses can be harmful to your health. Prolonged exposure to sewer odor can cause health troubles such as fatigue, dizziness, nausea, and even affect your memory.

If you are wondering what to do about sewer smell in the home, the first step is to identify the source and see what needs to be done next.

Let’s discuss.

How Does Sewer Gas Get Inside Your Home?

There are many ways in which sewer odor can creep into your home. Sewer gas can come from anything that’s attached to your sewer line. You must find the source(s) to properly remove the odorous gas.

Here are some of the most common causes for sewer gas leaks in a home.

1) Through the Toilet

Sewer smell enters through the toilet

The connection point around the base of the toilet will start to loosen over time. If the base of your toilet has cracks or is not sealed correctly, sewer gases from human waste will find their way through the crevices. The bacteria from this toxic waste can spread an odor throughout your home.

2) Up the Shower Drain

Odor up the shower drain

The shampoo and soap products that you wash down the shower drain can sometimes create a biofilm along your P-trap and pipes. Biofilm is a pinkish bacteria buildup that can cause illnesses and infections, as well as contribute to the formation of sewage gas. Biofilm can also accumulate in sink drains.

3) Clogged or Cracked Pipes

Woman looking at male plumber cleaning clogged pipes
Woman Looking At Male Plumber Cleaning Clogged Pipes

The awful sewer smell in the house can also be caused by pipes that are clogged, eroded, or cracked, which allows the odor to escape. Rotten and cracked pipes are common in older homes that have not had their plumbing updated. Pipe issues can also be caused by items that should not be flushed or poured down the drain. There can also be issues when a pipe collides with a growing tree root.

4) Broken or Missing Clean-Out Plugs

Pvc clean-out plug

Clean-out plugs are what separate the indoor from the outdoor sewer systems. These plugs are placed in sewage lines to block sewer gas from entering your home. If one of these plugs is missing or broken, it allows the foul smell to seep in.

5) Dry or Clogged Drain Traps

Avoid mess in kitchen sink

Drain traps help prevent gasses from entering a home. However, they can clog or dry out due to cold weather or poor air ventilation, allowing gas to flow back into the house.

6) Roof Vent Pipes

Roof vent pipes

Roof vent pipes allow gases to exit your home through your roof, instead of spreading elsewhere. When roofing vent pipes aren’t properly cleaned or experience corrosion, your home may trap the odor.

What are Simple Solutions for Identifying the Sewer Smell?

Once you find the source of the sewer odor, the next step is to rid the leaks from your home. You may be able to remove the smell of gas on your own, depending on the level of gas exposure in your home.

For example, if you think that a clogged drain is to blame, you can try flushing your pipes. You can flush your pipes naturally by removing the drain cover then slowly pour in about 1-2 gallons of boiling water, followed by a cup of vinegar, and lastly, a half cup of baking soda and more boiling water. This solution works to remove biofilm.

If the smell is coming from a weak toilet seal, then you can use caulk or another waterproof sealer around the base. If the toilet is cracked or difficult to seal, you may need to have it repaired or replaced through a professional plumbing service.

If the smell only emits when you are using hot water, such as while using the sink or shower, then you may have an overgrowth of bacteria in your water heater. One way to kill this bacterium is to increase the water temperature for 24 hours and flush out your pipes, the way we discussed earlier. You can also have your water tested to see if any other bacteria or sulfides are present.

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What if this Simple Solution Doesn’t Work?

When your DIY remedies fail to make a difference in eliminating the sewer smell in your house, it’s a sign that you need professional help. Calling a plumber is the best way to make sure that the issue is taken care of once and for all.

The first step that the plumber will likely take to determine the source(s) of the leak is to conduct a smoke test. This is a simple process that involves blowing smoke and air into the sewer line, typically starting from the nearest manhole. This smoke will travel the path of least resistance and appear at the area of your home that is allowing the gas in. Thus, identifying where the gas is coming in from.

Here are the steps of a smoke test:

  1. Identify testing areas: The areas of a sewer system that will be tested are often where rain and moisture flow through.
  2. Prepare: Plumbers will notify the neighborhood several days in advance of the smoke test to answer any questions or concerns they might have. They will also make certain that the plumbing crew is properly trained and obeys all safety protocols.
  3. Search for Smoke: The next step is to look for smoke coming from a home’s roof vent.
  4. Identify Defects: The non-toxic smoke will then help the plumber to identify any defects on the public side of the sewer system. Next, plumbers will search for defects within the home.
  5. Document: All defects are flagged and recorded.
  6. Report: Plumbers take photos and notes to gather all the details needed to permanently remove the gas leak from a home.

Once the plumber finds the source of the smell, they will provide solutions such as pipe and trap replacements or resealing.


If you have noticed a sewer smell in your house, it’s important to find the source as it could be sewer gas. Anything that is connected to the sewer line could be to blame, so it’s important to check all potential areas.

If you believe that you have found the source of the gas leak, you can try to rid the smell on your own. However, if your DIY techniques fail to work then you will want to hire plumbers to remove the odor.

You need a plumbing service that you can trust to get the job done. Duncan Plumbing, located in Santa Cruz, CA, is made up of a team of plumbers with years of experience. If you need help removing sewer gas from your Santa Cruz home – or any other plumbing services – give us a call at (831)-476-1712 or contact us online!

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