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How Do You Get Sewage Smell Out of a Finished Basement?

Last updated October 26, 2026

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The short answer

Find the Source First

A sewage smell in a finished basement usually means raw sewage or wastewater is seeping in somewhere. Check the toilet base for a loose wax ring, look for cracks in the floor drain, and inspect the vent pipe on the roof for blockages. A clogged vent can trap gases inside, pushing the odor back into your living space.

If you have a floor drain, pour water down it regularly to keep the trap full. A dry trap lets sewer gas rise straight into the room. In Port St. Lucie's humid climate, moisture can also hide the source, so use your nose and a flashlight to trace the strongest odor.

  • Check the toilet base for a loose wax ring
  • Look for cracks in the floor drain
  • Inspect the vent pipe on the roof for blockages
  • Pour water down floor drains weekly to keep traps full
  • Use a flashlight to trace the strongest odor

Clean Every Surface

Once you find the source, stop the leak if you can. Turn off the water supply to the toilet or fix the drain issue. Then clean all hard surfaces with a disinfectant that kills bacteria, like a bleach solution or a commercial sewage cleaner. Wear gloves and a mask, and open windows for fresh air.

Wash walls, floors, and any non-porous items thoroughly. Pay attention to baseboards and corners where residue can hide. Rinse with clean water and dry everything completely. A wet vacuum or a dehumidifier helps pull moisture from the air, which speeds up drying and reduces lingering odors.

Remove Porous Materials

Carpet, drywall, and insulation soak up sewage and hold the smell even after cleaning. If the contamination is heavy, these materials often need to be cut out and replaced. You can test a small area by wiping it with a damp cloth and smelling it after it dries. If the odor stays, the material is likely beyond saving.

Removing water-damaged drywall and flooring is messy work. You may need to tear out the bottom two feet of drywall, pull up carpet and padding, and dispose of them properly. This step is critical because sewage contains bacteria and can cause health issues if left in place.

Dry and Deodorize

After cleaning and removing porous materials, focus on drying the space completely. Use fans, a dehumidifier, and open windows to lower humidity. In a humid climate, moisture can slow drying and allow mold to grow on top of the sewage residue. Aim for dry air and surfaces.

For deodorizing, you can use an enzymatic cleaner that breaks down organic waste. Place bowls of baking soda or activated charcoal around the room to absorb residual smells. These are temporary fixes, though. If the odor remains after a few days, you may have missed a hidden source or need professional help.

When to Call the Pros

If the smell persists or the sewage backup was large, you might need professional help. Local water damage pros have the equipment to extract water, remove contaminated materials, and sanitize the area thoroughly. They can also identify hidden leaks in walls or under floors that you might miss.

For a finished basement, the cleanup can be complex because you have to protect the structure and your health. If you notice signs of mold or if anyone in the home feels unwell, see a doctor and consider calling a mold professional. Act quickly to prevent further damage and health risks.

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Phones are answered 24/7 for Port St. Lucie and nearby communities.

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Frequently asked questions

Why does my basement smell like sewage even after cleaning?

The smell often comes from a hidden source, like a cracked pipe or a dry drain trap. Porous materials such as drywall and carpet can absorb sewage and release odor over time. If cleaning doesn't work, you may need to remove those materials or call the pros.

Can I use bleach to get rid of the sewage smell?

Bleach can disinfect hard surfaces and kill bacteria, but it doesn't remove the source of the odor. You need to clean the area thoroughly first, then dry it completely. For porous materials, bleach may not penetrate deep enough, so replacement is often necessary.

Is it safe to stay in a basement with a sewage smell?

Sewage contains harmful bacteria and gases that can cause health problems, especially with prolonged exposure. If the smell is strong, leave the area and ventilate. See a doctor if you feel unwell. Professional cleanup may be needed to make the space safe again.

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