Fast Plumbing Answers: Laundry Room Smells Like Sewage?

Your laundry room should smell fresher than any room in the house. But yours smells like rotten eggs and sewage. It’s normal to worry, but you don’t have to- nine times out of ten, you’ll be able to fix this problem yourself.

Don’t worry: we’ll show you how to solve it in 3 minutes or less.

A laundry room that smells like sewer gas isn't just unpleasant- it means your drainage system isn’t flowing properly. But most of these smells are caused by a lack of water, not a broken pipe. You can usually solve this with a gallon of tap water and sixty seconds of your time.

Here's why your laundry room smells like sewage, how to fix it fast, and when you need professional help.

Laundry room smells won't go away in Dallas? Call Mother 24/7 for drain cleaning service.

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Dry P-Trap: The #1 Cause of a Stinky Laundry Room

The most common reason your laundry room smells like rotten eggs is a dry P-trap in your floor drain. The P-trap is a U-shaped pipe under your drain that holds water. That water creates a seal that blocks sewer gas from flowing up through the drain and into your laundry room.

When the P-trap dries out- which happens when the floor drain doesn't get used for a few weeks- the water seal disappears. Sewer gas flows freely up through the drain, and your laundry room smells like sewage.

This is especially common in laundry rooms with floor drains that rarely see water. Your washing machine drains into a standpipe or utility sink, not the floor drain, so the floor drain sits unused and the P-trap evaporates over time.

The 60-Second DIY Fix

Run water down the floor drain for 60 seconds. This refills the P-trap and restores the water seal that blocks sewer gas. If the smell goes away and stays gone, you've solved it.

To prevent the smell from coming back, pour a gallon of water down the floor drain once a month. This keeps the P-trap full and maintains the seal.

Dry P-traps can make any drain smell. Learn why they’re a leading cause of smelly sink drains.

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Not The P-Trap? Check Your Washer Hoses

If your laundry room P-trap is full and you still smell sewage, check your washing machine hoses. The rubber hoses that connect your washer to the water supply and drain line collect soap scum, lint, mold, and bacteria over time. This buildup smells terrible- a musty, sewage-like odor that gets worse when you run a load.

The smell comes from stagnant water and organic matter sitting in the hose folds and along the interior walls. Heat from hot water laundry cycles activates the bacteria and makes the smell stronger.

How to DIY Clean Your Washer Hoses

Detach the drain hose from your washing machine and inspect the interior. If you see black slime, mold, or buildup, clean it thoroughly with hot soapy water and a long brush or replace the hose entirely. Hoses are inexpensive and replacing them eliminates the smell immediately.

If your washing machine has a drain pump filter, clean that too. Buildup in that filter adds to septic smells in the laundry room.

Notice a similar smell in the bathroom? Follow expert steps in this companion guide.

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Two Causes That Require a Plumber: When DIY Fails

If you've refilled the P-trap and cleaned your washer hoses and your laundry room still smells like rotten eggs, it's time to call a plumber. Here are the two issues they'll check for.

Clogged Drain Line From Washing Machine

Your washing machine drains into a standpipe or utility sink that connects to your home's main drain line. Over time, lint, soap scum, and detergent residue build up inside this drain line and create a partial blockage. Wastewater sits in the clog and decomposes, releasing sewer gas that backs up into your laundry room.

A plumber will run a mechanical auger (professional-grade sewer snake) through the line to break up the clog and remove the buildup, then flush the line with water to restore full flow.

Baking soda and vinegar don’t work here. Online DIY guides love offering this solution because it looks great- tons of fizzing and liquid moving down the pipe. But this combo can’t break down lint or soap scum. You need a professional plumbing auger.

Laundry Room Vent Blockage

Your plumbing system includes vent pipes that extend through your roof. These vents allow sewer gas to escape outside and help water drain properly by letting air into the system. 

When a laundry room vent pipe gets blocked by debris, a bird's nest, or ice, sewer gas can't vent properly and backs up into your laundry room instead.

A plumber will inspect your vent pipe from the roof, clear any blockages, and verify proper airflow. If the vent is damaged or cracked, they'll repair or replace the affected section.

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The Solution: P-Trap, Washer Hoses, Then Call a Plumber.

Your laundry room smells like sewage because your floor drain P-trap is dry, your washer hoses are moldy, your drain line is clogged, or your vent pipe is blocked. The most common cause- a dry P-trap- is a 60-second DIY fix. Pour water down the floor drain and the smell goes away.

If that doesn't work, check your washer hoses for buildup. Still smelling sewage? Call a plumber to clear your drain line or inspect your vent pipe.

If you’re in the Dallas-Fort Worth Metroplex, take advantage of our fixed-price drain cleaning service. Mother offers a 120-Day Clog Free Guarantee with every service.

Does your DFW laundry room smell like eggs? Call Mother 24/7 for drain cleaning solutions that last. 

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