Why your house
smells like sewage
Most of the time this is a dried-out drain trap and you can fix it yourself in under a minute. Occasionally it is a sign of something you should not live with.
Start with the free fix
Every drain in your house has a P-trap — the U-shaped bend under the fixture. It holds a small amount of water permanently, and that water is the only thing standing between your nose and the sewer.
If a drain goes unused for a few weeks, that water evaporates and the seal is gone. Sewer gas comes straight up the pipe.
Try this first — it costs nothing
- Run water down every drain for 60 seconds. Including the guest bathroom, the basement floor drain, the laundry sink and the shower nobody uses.
- Flush every toilet, including ones rarely used.
- Wait a couple of hours and see whether the smell has gone.
This solves a large share of sewer smells, particularly in guest bathrooms, holiday homes, basements and anywhere after a long absence. Floor drains are the most common culprit because nobody ever thinks to run water into them.
If that doesn't fix it
Work through these in order of how likely and how cheap they are.
A failed toilet wax ring
The seal between the toilet base and the floor flange degrades over time. The smell is strongest right at the base of the toilet, often worse after flushing, and the toilet may rock very slightly. It's a routine repair.
A blocked or frozen vent stack
Your drains need air. The vent pipe running up through the roof lets air in so water can flow and gas can escape above the house. Block it — with a bird's nest, leaves, or ice in winter — and the system pulls air through the nearest trap instead, dragging gas with it.
The signature is gurgling drains plus smell. If you hear gurgling when another fixture drains, suspect the vent.
A cracked or disconnected drain line
Smell in a basement, crawl space or from a specific wall, with no obvious fixture cause. This is the one worth acting on, because a leaking waste line is depositing sewage inside the structure.
Water on the floor right now?
One call connects you with a local plumber taking emergency work.
Call 1-877-916-1136 Free to call · 24 hours · No obligationWhen it's more than a nuisance
Get it looked at promptly rather than living with it if you notice any of these:
- The smell is strong and persistent rather than faint and occasional
- Anyone in the house has unexplained headaches, nausea or dizziness
- It's accompanied by slow drains or gurgling — suggests a system problem
- There's damp or staining on a wall, ceiling or floor near the smell
- You smell it outdoors near the foundation — possible broken buried line
Sewer gas is mostly methane and hydrogen sulphide. At the concentrations produced by a dry trap it's unpleasant rather than harmful. At the concentrations produced by a broken line in an enclosed space it is neither of those things.
What won't fix it
- Air freshener. Masks a symptom that's telling you something.
- Bleach down the drain. Doesn't reseal a trap and doesn't repair a vent.
- Chemical drain cleaner. Wrong problem entirely — a smell is not a clog.
One thing worth doing anyway
If you have a floor drain or a bathroom you rarely use, pour a jug of water down it every couple of months, and add a splash of cooking oil. The oil floats on the trap water and slows evaporation considerably. It's an old trick and it prevents the whole problem.
Not urgent? Get a quote instead.
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