Sewer smell in your house: where it's coming from and how to stop it
Last reviewed · Not medical advice
Sewer smell means gas from the drain system is getting past a seal it shouldn't. Most of the time the cheapest seal has failed: a drain trap that dried out, slime in a sink drain, or the wax ring under a toilet. Work in that order — refill every trap, clean the smelly drain, check the toilet base — before suspecting vents or a broken sewer line. A plumber or a camera or smoke test finds what's left.
Most likely causes
Ranked for this situation. Open any cause for checks and fixes.
- 1
Dried-out drain trap
most commonGuest baths, basement floor drains, and unused showers are the classic spots.
Points to this:- Smell is near a guest bath, basement floor drain, unused shower, or utility sink
- Started after a trip, or in a room nobody uses
- Goes away after running water
Check it, fix it, who to call
Safe checks- Run water in every sink, tub, and shower for 30 seconds, and pour a bucket of water into floor drains.
- Flush toilets that rarely get used.
- Wait a few hours. If the smell is gone, it was a dry trap.
Fix- Run water in rarely used fixtures every couple of weeks.
- For floor drains that dry out constantly, a plumber can fit a trap primer or a trap-seal insert.
DIY stops here: If refilling the traps doesn't stop it within a day, the problem is past the trap — call a plumber.
Who fixes it: Plumber
More on this - 2
Slime in a sink drain or overflow
most commonIf the smell sits right at one sink or shower drain.
Points to this:- Smell is right at one sink or shower, strongest with your nose at the drain
- The drain is slow
- The overflow hole under the sink rim smells when you sniff it
Check it, fix it, who to call
Safe checks- Sniff the drain opening, then the overflow hole, separately.
- Pull the pop-up stopper — it's often coated in sludge.
Fix- Clean the stopper; scrub the drain and overflow with a long brush.
- Flush with very hot water. Use an enzyme drain cleaner for ongoing buildup.
DIY stops here: If cleaning doesn't change the smell, look for a trap or vent problem.
Who fixes it: You (DIY)
More on this - 3
Failed toilet seal (wax ring)
commonWithin daysSmell at the toilet base, sometimes a rocking toilet or stained floor.
Points to this:- Smell strongest at the toilet base
- Toilet rocks, or there's staining or soft flooring around it
- Water seeps from the base after flushing
Check it, fix it, who to call
Safe checks- Smell right at the floor joint around the toilet.
- Gently rock the toilet: any movement suggests a broken seal.
- Check the ceiling below an upstairs toilet for stains.
Fix- Pull the toilet and replace the wax ring (or a wax-free seal); tighten the closet bolts.
DIY stops here: A handy homeowner can swap a wax ring. A rotted subfloor or cracked flange needs a plumber.
Who fixes it: Plumber
More on this - 4
Blocked or damaged plumbing vent
commonWithin daysGurgling drains and smell in several rooms.
Points to this:- Drains gurgle or bubble, especially when a toilet flushes
- Water levels in toilet bowls drop or fluctuate
- Smell in several rooms, worse on windy days
Check it, fix it, who to call
Safe checks- Flush a toilet and listen at nearby sinks and tubs for gurgling.
- Look at the roof vent from the ground with binoculars for a nest or debris (don't climb onto the roof).
Fix- A plumber clears the vent stack or repairs a cracked or disconnected vent pipe.
DIY stops here: Roof work and snaking vents are a job for a plumber.
Who fixes it: Plumber
More on this - 5
Sewage ejector or sump pit
commonWithin daysBasement bathrooms that drain into a pumped pit.
Points to this:- Smell centered on a basement pit with a lid
- Pump runs constantly or not at all
Check it, fix it, who to call
Safe checks- Check that the ejector lid is bolted down with its gasket in place.
- Pour water into a dry sump pit to see if the smell eases.
Fix- Reseal the lid; make sure the pit vent runs outdoors.
- Have a plumber service or replace a failing ejector pump.
DIY stops here: Opening a sewage ejector pit or servicing its pump is a plumber's job.
Who fixes it: Plumber
More on this - 6
Front-load washer gasket or drum
less commonLaundry-room sewage smell is often the washer or its standpipe.
Points to this:- Clothes smell musty right out of the washer
- Dark residue in the folds of the door gasket
Check it, fix it, who to call
Safe checks- Pull back the gasket folds and look; smell the detergent drawer.
Fix- Clean the gasket and drawer; run the washer's cleaning cycle.
- Leave the door and drawer open between loads.
DIY stops here: Persistent smell after cleaning can be a slow drain or the drain pump — appliance repair.
Who fixes it: Appliance repair
More on this - 7
Cracked or leaking sewer line
less commonWithin daysWhen everything above checks out and the smell persists.
Points to this:- Persistent sewer smell that refilling traps doesn't touch
- Damp spots, stains, or lush grass along the sewer line route
- Recurring backups or slow drains throughout the house
Check it, fix it, who to call
Safe checks- Rule out traps, wax rings, and vents first.
- Look for wet areas in the crawlspace or basement along drain pipes (from a safe vantage point — don't crawl through sewage).
Fix- A sewer specialist runs a camera inspection or smoke test to find the break.
- Repair by spot dig, pipe lining, or replacement.
DIY stops here: Locating a hidden line break needs camera or smoke-test equipment.
Who fixes it: Sewer / drain specialist
More on this - 8
Septic system problem
less commonWithin daysSeptic homes: outdoor smell, soggy ground, slow drains house-wide.
Points to this:- On a septic system
- Smell outdoors over the tank or drain field, soggy ground, or slow drains house-wide
Check it, fix it, who to call
Safe checks- Check when the tank was last pumped; look for pooling water over the drain field.
Fix- Have the tank pumped and inspected; a septic contractor assesses the drain field.
DIY stops here: Never open a septic tank or enter one — its gases can be deadly.
Who fixes it: Sewer / drain specialist
More on this
How we rank causes: by how often each one explains this smell in ordinary homes, according to plumbing, HVAC, electrical, and building-science guidance, adjusted for the context on this page. The labels are judgments, not measured statistics. Anything dangerous that can't be ruled out (gas, fire, electrical) is covered in the safety box at the top of the page, whatever its rank.
Which one is it?
| Clue | Points to | Fix level |
|---|---|---|
| Unused bathroom or floor drain; gone after running water | Dry trap | DIY, 5 minutes |
| Strongest with your nose at one drain or overflow | Drain slime | DIY cleaning |
| At the toilet base; toilet rocks or floor is stained | Wax ring | DIY or plumber |
| Drains gurgle when a toilet flushes | Blocked vent | Plumber |
| Basement, near a lidded pit | Ejector or sump pit | Plumber |
| Persistent everywhere; damp spots along pipes | Cracked line | Camera or smoke test |
| Outside, soggy ground over the tank or field | Septic | Septic contractor |
Narrow it down
Answer in order. Stop at the first yes.
- 1Does running water in every fixture make it go away within a few hours?Yes → Dry trap. Run water in rarely used drains every couple of weeks.No → Keep going.
- 2Is it strongest at one drain or the sink overflow hole?Yes → Clean the stopper, drain, and overflow. Enzyme cleaner for buildup.No → Keep going.
- 3Is it strongest at a toilet base?Yes → Check whether the toilet rocks, then replace the wax ring.No → Keep going.
- 4Do drains gurgle, or do toilet water levels change by themselves?Yes → A vent is likely blocked — call a plumber.No → Ask a plumber for a camera inspection or smoke test of the lines.
Safe checks you can do yourself
In the order that finds the source fastest.
- 1
Refill every trap in the house
Run each sink, tub, and shower for 30 seconds, flush every toilet, and pour a bucket of water into basement floor drains and laundry standpipes.
- 2
Find the strongest spot
After refilling, walk the house. Smell at drain openings, at toilet bases, and under sinks. The source is usually within a few feet of where it's strongest.
- 3
Toilet check
Gently push the toilet side to side. Any rocking, a stained or soft floor, or water at the base after flushing points to a failed seal.
- 4
Listen for gurgling
Flush the toilet and listen at the nearest sink and tub. Gurgling or bubbling means the drain system isn't venting properly.
- 5
Basement pits
If there's a sewage ejector pit, confirm the lid is bolted down with its seal intact. Don't open it.
Sewer smell in the bathroom only
Bathrooms concentrate the cheap failures: a shower trap that dried out, a sink overflow full of slime, a toilet seal that gave up. Check in that order. If a bathroom smells right after someone showers in the next room, suspect a vent problem, because fixtures sharing a drain can pull each other's traps dry.
Why vinegar and baking soda only sometimes work
They can loosen light buildup in a drain, so the drain-slime cause sometimes improves. They do nothing for a dry trap (water does), a failed toilet seal, a blocked vent, or a cracked line. If the smell returns within days, move on to the next check.
When DIY stops
- Sewage backing up anywhere in the house.
- Gurgling drains or a suspected vent blockage — roof work is a plumber job.
- The toilet flange is cracked or the floor around it is soft.
- Traps, drains, and toilet are ruled out and it still smells — it needs a camera or smoke test.
- Anything involving opening a septic tank or ejector pit.
Who to call
- Plumber
Toilet seals, vents, ejector pumps, trap primers, and backups.
Drains, traps, toilets, vents, water heaters, and leaking supply lines.
- Sewer / drain specialist
Camera inspection or smoke test to find a hidden line break.
Camera inspection and smoke testing of sewer lines and vents.
- Water damage / restoration company
Sewage soaked flooring or drywall — contaminated materials need proper removal.
Finds wet materials with moisture meters and dries structures out.
- Your gas utility's emergency line
It might be gas: a rotten-egg smell near a gas appliance.
Checks for natural gas leaks. Call its emergency number, not the billing line.
Answer a few questions about where and when you smell it. You'll get the causes ranked for your situation.
Frequently asked questions
Why does my house smell like sewage all of a sudden?
Usually a trap dried out — after a trip, or in a bathroom nobody uses — or something changed in the drains, like a clog that's starting to siphon traps. Refill every trap first; it's the cheapest test.
Is sewer gas in the house dangerous?
A faint whiff from a dry trap is mainly a nuisance and a sign of a broken seal. A strong smell, or people feeling unwell, is different: ventilate, get out, and call for help. Never enter a septic tank or pit.
Why does my basement floor drain smell like sewage?
Floor drains are rarely used, so their trap water evaporates. Pour in a bucket of water. If it keeps drying out, a plumber can install a trap primer or a trap-seal insert.
Can a plumber find a sewer smell?
Yes. Beyond checking traps and seals, plumbers and drain specialists use cameras inside the lines and smoke tests, which push harmless smoke into the system so it shows up wherever gas escapes.
Related smells
Sources
- Carbon Monoxide Information Center — U.S. CPSC