Sewer Smell in the House: What to Do Right Now
A rotten-egg or sewage smell indoors is unpleasant, but it's usually not an emergency — and the most common cause is the cheapest one to fix.
Before assuming a broken line, rule out a dried-out drain trap. The steps below walk through the honest, in-order checks a plumber would start with.
If this is unsafe or getting worse right now, don't wait — call and we'll route you straight to an independent local pro.
What to do in the first 5 minutes
- Run water for 30–60 seconds in every sink, tub, floor drain, and rarely-used bathroom — a dry P-trap lets sewer gas up through the drain and is the #1 cause.
- Pour a cup of water into floor drains in the basement, garage, or laundry that seldom get used.
- Open windows and run exhaust fans to clear the air and confirm whether the smell comes back after the traps refill.
- Sniff around to locate the source: a single room usually means a local trap or wax ring; a whole-house or outdoor smell points further down the line.
- If the smell persists after every trap is refilled, note where it's strongest and call a local sewer pro to inspect.
Do not do this
- Never ignore a persistent sewer-gas smell paired with a headache, dizziness, or nausea — leave the area, ventilate, and seek fresh air; sewer gas can contain methane and hydrogen sulfide.
- Never mix drain chemicals (like bleach and ammonia-based cleaners) trying to kill the odor — the fumes can be dangerous.
- Don't open or dig at a suspected sewer cleanout or line yourself — sewage is contaminated Category 3 water.
- Don't light candles or use open flames to mask the smell if you suspect gas.
What's likely going on
Dried-out drain trap (most common)
Every drain has a water-filled U-bend that blocks sewer gas. In a guest bath, floor drain, or unused fixture the water evaporates and the smell rises. Running water refills it — often the whole fix.
Failed toilet wax ring
A toilet that rocks or leaks at the base can let gas escape around a dried or broken wax ring. It's an inexpensive plumber fix, usually $100–$250.
Blocked or clogged plumbing vent
The roof vent lets sewer gas escape upward. A nest, leaves, or ice can block it and push gas back into the house. A pro can clear the vent stack safely.
Cracked or broken sewer line
A cracked lateral or a broken seal underground can seep gas up through the slab or yard. Only a camera inspection can confirm this — it's the least common but most serious cause.
Diagnose it now
What it typically costs
Refilling traps is free, and a plumber visit to chase down a wax ring or persistent odor is often $100–$250. If a camera inspection is needed it runs $125–$500, and any actual line repair is a separate quote, commonly $1,500–$7,000. Only a camera can confirm a broken line — most sewer smells never get that far.
Frequently Asked Questions
Why does my house smell like sewer but there's no obvious leak?
The usual culprit is a dried-out drain trap in a rarely-used fixture or floor drain, letting sewer gas up through the drain. Run water in every drain for a minute. If the smell clears, that was it — no leak involved.
Is a sewer smell in the house dangerous?
An occasional whiff from a dry trap is a nuisance, not a hazard. But a strong, persistent sewer-gas smell can contain methane and hydrogen sulfide — if it comes with headaches or dizziness, ventilate, leave the area, and get it inspected.
How do I find where the sewer smell is coming from?
Smell room by room. A single bathroom points to a local trap or the toilet's wax ring; a whole-house or outdoor smell suggests a vent or line problem. If refilling every trap doesn't fix it, a pro can pinpoint it with a camera.
The service that handles this
Guidance only — independent local providers assess and price their own work. Last reviewed 2026-07.
Prefer to just talk to someone?
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