A sewage smell should fade within days of a complete cleanup, so one that lingers means a source is still in the building. The usual causes are contaminated material left behind, wet subfloor or wall cavities, mold, a dry or failed trap, or an unrepaired plumbing fault. The odor goes away only when the source is removed and the structure is dried, with deodorizing as the last step.
How Long Should a Sewage Smell Last After Cleanup?
A sewage smell should fade within a few days of a complete cleanup and drying; a smell that lasts longer means a source is still there. The smell comes from contaminated material and moisture, not from the air itself. Once both are gone, fresh air clears what remains.
A smell that grows stronger on hot days or with the AC off points to a wet material releasing odor as it warms. Gilbert summers make a hidden source easy to notice.
Humidity plays a part too. Gilbert’s monsoon season raises indoor humidity, and damp material releases more odor, so a faint smell that returns in summer still points to something left behind.
The 5 Reasons a Sewage Smell Won’t Go Away
The 5 reasons a sewage smell won’t go away are contaminated material left behind, wet subfloor or wall cavities, mold growth, a dry or failed trap, and an unrepaired plumbing fault. Each one has a simple check.
- Contaminated material left behind: carpet pad, baseboards or drywall the cleanup kept. Check by smelling at the base of each wall in the backup room.
- Wet subfloor or wall cavity: water sealed under flooring or behind drywall. Check with moisture readings against a dry reference spot.
- Mold growth: a musty smell rather than a sewage one. Check the wettest readings first.
- Dry or failed trap: a P-trap that evaporated or a toilet wax ring that leaks. Check by pouring water into floor drains and rocking the toilet.
- Unrepaired plumbing fault: the cracked line or blockage that caused the backup. Check with a plumber’s camera inspection.
The EPA notes that a house not dried out properly develops a musty odor signifying microbial growth (EPA). That is why reasons 2 and 3 usually appear together.
How Is a Lingering Sewage Odor Removed?
A lingering sewage odor is removed by finding and removing the contaminated material, drying the structure and then deodorizing, in that order. Deodorizing before source removal only covers the smell for a few days.
- Source removal: cutting out the soaked drywall, pad or baseboard holding the residue
- Cleaning and disinfecting: treating the framing and slab the removed material exposed
- Structural drying: running air movers and dehumidifiers until moisture readings return to normal
- Deodorizing: hydroxyl generators or thermal fogging to neutralize the residual odor
Crews that offer sewage odor removal and deodorizing follow the same sequence. Deodorizing is the final step, never the first.
Check the HVAC system as well. A return vent near the backup room can pull contaminated air into the ducts, which spreads the smell to rooms the sewage never reached.
Do air fresheners or fogging remove sewage odor?
No, air fresheners and fogging mask a sewage odor until the source is removed. Thermal fogging does neutralize residual odor once contaminated material is gone. The EPA warns that ozone generators are generally ineffective against odor-causing chemicals at safe levels and can damage the lungs (EPA).
When the Smell Comes From Mold, Not Sewage
Sometimes the smell changes from sewage to musty a week after cleanup. That shift means the contamination is gone but moisture stayed and fed mold. Mold that keeps a smell going needs its own removal and drying.
How Do You Tell Mold Odor From Sewage Odor?
The key difference between mold odor and sewage odor is that mold smells musty and earthy while sewage smells like rotten eggs or waste. The type of smell points to where you look.
| Smell | Likely source | Where to check | Next step |
|---|---|---|---|
| Rotten eggs at a drain | Dry trap or sewer gas | Floor drains, unused sinks, toilet base | Refill traps; check the wax ring |
| Waste smell in the backup room | Contaminated material left behind | Base of walls, baseboards, carpet pad | Remove the material |
| Musty, earthy smell | Mold from slow drying | Wall cavities, under flooring, cabinet bases | Moisture readings, then removal |
| Smell after the AC runs | Contaminated ductwork or a wet air handler area | Return vents near the backup room | Duct inspection and cleaning |
| Smell that returns with each flush | Unrepaired line fault | Main line and cleanout | Camera inspection |
Two smells at once usually means two problems: a source still in place and moisture still feeding mold.