Sewer smell in the house. Here's where it's actually coming from.
Sewer gas smells like rotten eggs, and it means something is open between your drains and your nose. Work these three checks in order — the first one fixes most cases for free, and we'll tell you exactly when the smell means a real problem.
What you'll need
Most of this is already in the house:
- Your nose — figure out which drain or room smells worst
- Water — for refilling dry traps, about 30 seconds per fixture
- A teaspoon of cooking oil — slows evaporation in floor drains
- About 15 minutes — this is a quick hunt, not a project
The 3 checks, in order.
Start with the free fix — it solves most sewer smells. Move down the list only if the smell survives.
Refill every dry P-trap
The most common cause, and the free fix: a guest bathroom, floor drain, or laundry standpipe that hasn't been used in weeks. The water in the trap evaporates, and sewer gas walks right in. Run water in every sink, tub, and floor drain for 30 seconds. For floor drains, pour a bucket of water with a teaspoon of cooking oil — the oil slows the next dry-out.
Check the toilet base
If the smell is strongest near a toilet, rock it gently. A wobbly toilet means the wax ring underneath has failed — sewer gas (and water) escape around the base. Look for staining or softness at the base. Resetting a wax ring is a cheap fix; ignoring it rots the floor underneath.
Check the roof vent
Every drain system breathes through a vent pipe on the roof. If it's blocked — bird nest, leaves, debris — pressure builds and pushes gas through the traps. Gurgling drains plus the smell is the classic signature. Check from the ground with binoculars, and stay off a steep or wet roof — we check vents on every service call.
Skip this: air fresheners and bleach.
They cover the symptom and teach you nothing. Here's the honest version.
Air fresheners just mask it
Plug-ins and sprays don't touch the source — an open path between your sewer and your air. The smell comes back the moment the spray fades, and you've learned nothing about where it's coming from.
Bleach doesn't seal anything
Pouring bleach down the drain kills odor for a day, but sewer gas comes from the sewer system, not from bacteria in the trap. Bleach in a dry trap evaporates just like the water did.
A smell that won't quit can mean a cracked line
If you've filled every trap, the toilets are solid, and the rotten-egg smell still hangs around — especially near one spot — it can be a cracked or broken sewer line venting gas into the house or under the slab. That's a camera job, not a candle.
When to call a plumber.
Did the checks and the smell is still there? That's when it stops being a DIY problem:
Smell won't quit
Filled every trap, checked the toilets, gave it a day or two — and it's still there. Time for a pro. We trace sewer gas to its actual source instead of guessing.
Multiple drains affected
Odor coming from several fixtures at once points past the traps — a venting problem or a mainline issue. We camera the line and check the vents.
Gurgling plus smell
Drains that gurgle while the smell shows up mean air is trapped or the line is partially blocked — a drainage problem, not just an odor problem. That's a plumbing repair call.
Sewer smell FAQ
Straight answers, no sales pitch.
Is sewer gas dangerous?
In large amounts, yes — it contains methane and hydrogen sulfide. The rotten-egg smell is a warning your nose is built to catch. A faint occasional whiff from a dry trap isn't an emergency; a strong, constant smell deserves a prompt call.
Why does only one bathroom smell like sewer?
Usually a dried-out trap in that bathroom's tub or floor drain, or a failing wax ring under that toilet. Fix the fixture, fix the smell. If it's the least-used bathroom in the house, bet on the trap.
Can a clogged roof vent cause sewer smell?
Yes. A blocked roof vent stops the system from breathing, pressure builds, and gas pushes through the weakest trap. Gurgling drains plus odor is the classic vent-blockage signature.
I smell sewage in the yard — is that normal?
A faint whiff near a cleanout cap can be normal. Strong sewage odor in the yard, soggy spots, or lush green patches over the sewer line are not — that can mean a break in the line, and it's a camera-inspection job. Call (818) 669-9019.
Smell that won't quit?
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