You walk in and there it is — that unmistakable smell. It might be faint. It might be overwhelming. Either way, your gut is telling you something is wrong.
Your gut is right. Here’s how to figure out what you’re dealing with.
Sewage smell inside a house means one of a few things is happening — and none of them get better on their own. The smell is either sewer gas leaking into your living space, a drain backing up before you can see it, or active sewage already inside a wall or under a floor.
Sewer gas contains hydrogen sulfide and methane. At low concentrations it smells terrible. At higher concentrations it’s toxic, and it’s flammable. This is not a “wait and see” situation.
Near a floor drain or infrequently used sink or tub: This is often a dried P-trap. The curved pipe under every drain is designed to hold a small amount of water that blocks sewer gas from rising into the room. If a drain doesn’t get used for weeks or months, that water evaporates and the seal is gone. Pour a cup of water down the drain and see if the smell clears within a few hours.
Near a toilet: Could be a failed wax ring — the seal between the toilet base and the floor drain. If the toilet rocks even slightly when you sit on it, the wax ring may be broken. This is a plumber call, not a restoration call, but it needs to happen today.
Throughout the house, especially in the morning: A whole-house sewage smell — especially one that’s worse after rain or when toilets are flushed — often indicates a problem with the main sewer line or a vent pipe. Tree roots in Houston’s clay-heavy soil are notorious for infiltrating sewer lines, particularly in Meyerland, Bellaire, and older Montrose neighborhoods with mature trees and aging clay pipes.
Near walls, floors, or under cabinets: This is the one that requires urgent action. Sewage smell coming from inside a wall or under flooring usually means active sewage intrusion — a pipe has failed and the material inside is contaminated. This is a biohazard situation.
Get out and call for help if:
Hydrogen sulfide at even moderate concentrations causes headaches and nausea. At high concentrations it causes rapid incapacitation. Don’t try to investigate a strong sewage smell in a confined space.
The restoration industry classifies water damage by contamination level. Category 3 is the most severe — it includes sewage, floodwater from rivers and bayous, and any water that has mixed with biological waste. The IICRC S500 standard requires that Category 3 materials be treated as a biohazard: containment, full PPE, and proper disposal, not just cleanup and drying.
Houston’s bayou flooding events — like those during Harvey and the subsequent flood events in 2019 and 2021 — routinely introduce Category 3 water into homes because the bayou system connects to the municipal sewer. If your flooding came from outside during a storm, assume contamination.
Don’t run exhaust fans or your HVAC system to try to clear the smell. Fans spread contaminated air and potentially contaminated particles through the house and into the duct system. If sewage has physically entered the space, the HVAC system distributing that air makes the problem significantly worse and much more expensive to remediate.
Don’t use chemical masking sprays or plug-in deodorizers. The smell is a symptom. Masking it doesn’t address what’s causing it — and it makes it harder to track where it’s coming from.
Standard homeowners insurance does not automatically cover sewage backup. It requires a specific rider — often called “water backup coverage” or “sewer backup coverage” — that is sold as an add-on. Check your policy declarations page now.
If you don’t have the rider and sewage has entered your home, you’re likely paying out of pocket. Average sewage remediation costs in Houston range from $3,000 to $15,000 depending on the affected area and how long the material sat. This is not a DIY job — improper cleanup of sewage-contaminated material leaves behind pathogens including E. coli, hepatitis A, and norovirus.
A sewage smell that goes away quickly — especially near an infrequently used drain — may be a simple fix. A sewage smell that’s strong, persistent, or coming from walls or floors is not. Trust the smell. It exists because something has failed and contaminated material is present somewhere it shouldn’t be.
If the smell is serious or you can see any sewage backup, call 247 Restoration Specialists. We handle Category 3 biohazard cleanup across Houston 24 hours a day, and we’ll tell you straight what you’re dealing with before we recommend anything.
It depends on the source and intensity. A faint smell from a dried P-trap is generally not a health risk once water is added to the drain. A strong, pervasive sewage smell — especially one that causes nausea or comes from walls — is not safe. Leave and call a professional.
Heavy rain can overload the municipal sewer system, which pushes sewer gas back through household drain lines. It can also cause sewage to back up into homes through floor drains and low-point fixtures. Older neighborhoods with clay sewer laterals — common in Heights, Bellaire, and Meyerland — are especially vulnerable.
Sewage remediation in Houston typically costs between $3,000 and $15,000 depending on the affected area, how long the sewage sat, and whether structural materials like drywall and flooring need replacement. Costs rise significantly if the HVAC system was exposed to contaminated air.
