What is Sewer Gas?

What do plumbing leaks, cracked pipes, and clogged drains have in common? They all can produce sewer gas, a combination of toxic and non-toxic gases that create a foul-smelling mess for your home. If you’ve ever caught a whiff of an unpleasant odor when walking by your sink, you’ve likely smelled sewer gas. In this article, we’ll cover everything you need to know about sewer gas and how to get rid of it.

What is sewer gas? What does it smell like?

Sewer gas has a distinct and unmistakable odor. Sulfides, methane, and ammonia combine with other compounds to produce the smell, which is reminiscent of rotten eggs. The most common gases that comprise sewer gas include:

Hydrogen Sulfide

The primary gas found in sewage systems, hydrogen sulfide, is notably toxic in large quantities. When exposed for long periods of time, adverse symptoms can develop.

Methane Gas

While methane gas is nontoxic, it is responsible for the smell that’s characteristic of sewer gas. In large quantities methane is extremely flammable, which can make large quantities of sewer gas a possible fire hazard.


While ammonia is not the primary gas found in sewer gas, exposure to high levels of it can irritate the eyes, nose, and throat with a burning sensation.

Is sewer gas dangerous?

In small amounts, sewer gas is more of a nuisance than a true danger. However, in large quantities it can cause health problems. Exposure to high amounts of sewer gas can cause irritation to the eyes, nose, throat, and respiratory tract. Exposure symptoms can also include fatigue, headaches, and nausea. In severe and extremely rare cases, exposure to large amounts of sewer gas can cause organ damage or even death.

If you believe there’s a serious sewer gas leak in your home, consider it a plumbing emergency. Contact a plumber for advice on how to proceed safely.

What causes sewer gas in the home?

Before you can eliminate the source of sewer gas odors, you have to narrow down where exactly it’s coming from. Common causes of sewer gas include:


Sewer gas can enter the home through leaks in pipes and plumbing fixtures. Even the smallest leaks can turn into major ones and cause water damage, along with sewer-gas leakage. While it’s best to work with a plumber to address leaks, you can buy yourself some time by fixing minor leaks with DIY solutions.

Cracked pipes

The pipes in your home will likely degrade over time. This is especially true if you have an older home, particularly one that uses old piping materials like Orangeburg Pipes. Cracks, breaks, and gaps in pipes gives sewer gas a one-way ticket into your home.

Clogged drains

Drains have the important task of transporting water, waste, and other materials through the septic system. When drains become clogged, a sewage backup can occur. If you don’t treat the cause of the backup through safe drain-cleaning methods, the clog will continue to grow, and the concentration of sewer gas will increase.

Dry plumbing systems

When plumbing systems like your toilet and your sink drain aren’t used, they dry out and lose their water barrier. This barrier is essential in protecting against sewer gas. When plumbing systems dry out, sewer gas can leak into the house.

How to get rid of sewer-gas smell

Sewer gas can be a tricky odor to get rid of. Making it with air fresheners and candles won’t do much good in the long run, so it’s important to attack it at the source. In 8 Ways to Get Rid of Sewer Gas Smell, you’ll find a checklist of what you can do to banish sewer gas smell from your home, including:

  • Clean the sink overflow
  • Check the toilet wax ring
  • Caulk the toilet base
  • Clean drains
  • Check the P-trap under your sinks
  • Check for leaks
  • Clean garbage disposal splash guard
  • Call a professional for a video drain inspection

How to prevent sewer gas smell

When it comes to sewer gas smell, taking preventative measures can help keep the odors at bay. Here are two easy things you can do on a regular basis to keep your drains clean, and your plumbing system free of sewer-gas smells.

Keep your drains clean

Keeping your drains clean is the best defense against sewer gas. If your drains are full of organic matter build-up or soap scum, you’ve inadvertently created the perfect environment for sewer gas to thrive. Fortunately, it’s easy to clean out existing build-up and prevent it from recurring.

Baking soda and vinegar

The trusty non-toxic combo of baking soda and vinegar can clean drains naturally. Add one cup of baking soda to the clogged toilet or slow drain, then wait a few minutes. Follow with two cups of vinegar. Listen for bubbling and sizzling noises to indicate that the mixture is working. Wait another couple of minutes before either flushing the toilet or running water down the drain. If you still notice a smell, repeat the steps again.

Enzyme-based cleaners

Rather than using a liquid drain cleaner, which is more likely to hurt your drains than help them, we recommend that you use an enzyme-based cleaner. Instead of caustic chemicals, enzyme-based cleaners use good bacteria cultures and concentrated enzymes that naturally eat away at organic matter.

Keep water in P-traps

The P-trap is an upside-down question-mark shaped piece of PVC or stainless steel located underneath your sink that traps debris and prevents clogs. Usually, the P-trap is full of water. But, in a rarely used sink, this water can evaporate, allowing sewer gasses to escape up the drain and into the air. Make sure to run some water from your sink down the drain every now and again to keep the water from evaporating. You can also add a few tablespoons of vegetable oil along with the water to slow down evaporation.

Plumbing smells? Contact Chas Roberts

From sewer gas to bad-smelling tap water, trust Chas Roberts to conquer plumbing odors big and small. Contact us for all your plumbing needs.