What to Do If You Smell Sewer Gas (and How to Prevent the Issue)

Candace Nelson
Written by Candace Nelson
Updated February 11, 2022
PVC pipe with a standard sewer trap
Photo: Douglas Sacha/Moment/Getty Images

Smelling sewer gas can not only be unpleasant; it's dangerous

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If you catch a whiff of rotten egg smell in your house—and not because you haven’t taken out the compost in a while—you likely have a plumbing problem that needs attention.

The unpleasant smell is hydrogen sulfide, a gas that comes from decaying organic matter (the more polite term for raw sewage). Temporary, low-level exposure to some sewer gas can lead to eye irritation and respiratory issues that should go away when you get away from the gas. Here’s what you should do next.

What You Need to Know If You Smell Sewer Gas

Hydrogen sulfide is a colorless gas. Exposure can lead to eye irritation and respiratory issues like a sore throat and cough for all residents—including your pets. You don’t have to evacuate the premises, but maybe slide open a window or step away from the smell while you plan out your next steps.

Temporary exposure is typically not harmful, and the symptoms should go away soon after you step away. Long-term exposure to the gas, even at low levels, can have more dramatic symptoms, such as loss of appetite, fatigue, dizziness, and headaches. High levels of exposure would not be typical in a home.

But don’t delay fixing the problem. In addition to being unpleasant, sewer gases, including hydrogen sulfide, are explosive. The best course of action is to get away from the smell and call a local plumber immediately and get the problem taken care of.

When to Call a Plumber If You Smell Sewer Gas

If you’re smelling hydrogen sulfide, it could be a minor problem like a dried-out water seal in a floor drain. Or you could have a blocked, broken, cracked, or deteriorated pipe allowing the gas to enter your home. Either way, it’s not going to go away until it's repaired.

In homes, hydrogen sulfide is directed out through vents. If you smell something foul, it’s a sign you have a plumbing problem that needs attention. 

The smell is likely strongest at floor level or at the drain. While it might come and go (or you may become so used to it that you no longer notice it), it’s not fixed even if the smell dissipates for a while. 

A professional plumber can diagnose the problem and recommend a fix, so everyone in the house can breathe easily again.

Causes of Sewer Gas Smell

The most common cause of sewer gas smells in your house is a leak in your plumbing. You’ll want to prevent even small leaks to avoid major plumbing repair costs. Sewer gas smells could be coming from your pipes either because they weren’t installed properly or were damaged. A local plumbing professional can help to assess the problem. 

All plumbing fixtures should have a sewer gas trap installed (just one of the few plumbing terms it’s helpful to know). This part allows wastewater to leave the house but blocks sewer gases from getting in. Replacing one costs about $100 for materials and $45 to $200 per hour for a professional plumber’s time.

How to Prevent Sewer Gas Smells in Your Home

You can’t stop the ground from settling or the air from freezing, but you can take care of your plumbing. Keeping things flowing will prevent expensive backups and icky smells.

Prevent Clogs

Watch what goes down the drain or gets flushed. Use the compost pail for food scraps, paper towels and cooking oils that can clog a drain. Use the trash can rather than the toilet for things like feminine hygiene products and dental floss. For about $10, you can get a hair trap for your shower drain,  which will catch strands before they get caught in the pipes. 

The average cost to have a professional clear a clog is $215.

Run the Water

If you have a rarely used bathroom or sink, the pipes can get dry. It helps to use your plumbing fixtures occasionally in between house guests. When you don’t use a fixture, the trap that keeps sewer gases out can get dry. If the smell is coming from one drain or sink, run some water down it to see if that fixes the problem.

Clean the Drain

Even though you use your trash, compost pail, and hair catch, drains inevitably get backed up from soaps, lotions, detergent, beard trimmings, and whatever the kids put in there. If it starts to smell or the water drains slowly, you need to clean the drain. Most of the time, this can be accomplished by sliding a thin, flexible wire with a small hook at the end down the drain to grab the clog. You can buy a drain cleaning tool for about $5 at your local hardware store.

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