Repair guide
Sewer smell in the house
Updated 30 Sep 2026 · AR Logic LLC · 1 source
Usually not an emergency
A sewage or rotten-egg smell indoors is most often a drain trap that has dried out — in a guest bathroom, a basement floor drain or an unused shower — letting sewer gas past the water seal. Pour water into every drain that is rarely used; if the smell stays, the next suspects are a failed toilet wax ring, a blocked plumbing vent, or a cracked drain pipe.
Is a sewer smell in the house an emergency?
Usually not, but do not ignore it. If the smell is strong and anyone has a headache, dizziness or nausea, get fresh air. A rotten-egg smell can also be natural gas: if you have gas appliances and are not sure which it is, leave and call the gas company or 911 from outside.
Snap a photo — see what it is, how urgent, who to call.
One photo of the problem. fixRAgent reads it and gives you a Triage Profile.
Triage a photo nowNo sign-up.
Take the photo. We’ll tell you what it is.
No sign-up · AR Logic LLC · Privacy
Managing this for someone else? Managers: set it up for your buildings →
Managing this for someone else? There is a version of this for whole portfolios.
Managers: set it up for your buildings →What to check, in order
Refill dry traps
Run water for a minute in every sink, tub and shower you rarely use, and pour a bucket of water into floor drains. The U-shaped trap holds water that seals out sewer gas; it evaporates if the drain is not used.
The toilet base
A toilet that rocks, or a smell right at its base, points at a failed wax ring seal under it.
Plumbing vents
Gurgling drains together with the smell can mean the vent through the roof is blocked, so drains pull water out of their traps.
Sinks: the overflow and the pipe under it
Bacteria in a sink overflow or a loose joint under the sink can smell like sewage.
Cracked pipe or sewer line
A smell that persists with every trap full, especially in a basement or crawlspace, can be a cracked drain line — a plumber can smoke-test or camera the lines.
Safety first
- Sewer gas contains hydrogen sulfide — a toxic gas with a rotten-egg smell; at high levels a person can stop being able to smell it [1].
- Do not enter pits, sumps or confined spaces to find the source.
When to call a pro
Call a plumber if the smell continues with every trap full, the toilet base leaks, drains gurgle, or you see sewage.
What to photograph
For the Triage Profile, photograph the drain, toilet base or pipe nearest the smell, with any water or staining in view. One clear photo in good light is enough; the Triage Profile says what it is, how urgent it is (emergency, today, this week or whenever), and which trade to call.
Questions people ask
Why does it smell only sometimes?
Wind across the roof vent, or a trap that slowly evaporates between uses, makes the smell come and go.
Sources
Not sure what you’re looking at?
Snap a photo of it. The Triage Profile says what it is, how urgent it is, and who to call.