Why does my house smell like sewage?
Most often a drain trap has dried out in a fixture nobody uses, letting sewer gas in. Less often the plumbing vent on the roof is blocked, or the sewer line is damaged. A rotten-egg smell can also be natural gas: if you think so, leave the house and call 911 and the gas company. Otherwise, refill the traps first.
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By Kasra Taheri, Founder, LoclisPublished
Researched and drafted with AI, then checked claim by claim against the sources listed below before it was published. Prices and rules change; the dates beside each source say when it was last checked.
Step by step
Read when to stop and call a pro, further down this page, before you start.
Step 1: Rule out a gas leak
If the smell is sulfur or rotten eggs and you cannot link it to a drain, treat it as natural gas: go outside and call 911 and the gas company before anything else.[3]
Step 2: Find the strongest spot
Sniff in the bathrooms, kitchen and basement first, since that is where the county says to look for the source.[1]
Step 3: Refill seldom-used traps
Pour a gallon of water down the drains and sinks that are not used often.[1] Include guest baths, tubs, a basement floor drain and a laundry sink.
Step 4: Refill unused toilets
Add water to any toilet that is rarely used, flushing it if needed, so its water seal is full again.[1]
Step 5: Clean the kitchen drain
Run hot water and dish soap through the kitchen sink and disposal, since food residue gives off a sewage-like smell.
Step 6: Look for water or dampness
Check the floor around toilets and under sinks for wet spots, stains or soft flooring, which point to a leak rather than a dry trap.
Step 7: Walk outside
Check along the line from the house to the street for soggy ground, dark liquid or a sewage smell in one spot.[2]
Step 8: Recheck in a day
If every trap is full and the smell is gone, a dry trap was the cause. If it returns, move to the vent and sewer line checks below.
Start with the cheap cause: a dry trap
Most sewage smells inside a house come from a drain that has gone dry. Every sink, tub, shower and floor drain has a trap, a bend that holds water as a seal against the sewer. Sewer gas and odors could enter your home or business if any plumbing fixtures have not been used in a while and the water in the water-sealed traps has evaporated.[1]
Fairfax County's advice is simple. If you have a sewer odor in your home, first look for the source in the bathrooms, kitchen or basement.[1] Then pour a gallon of water down the drains and sinks that are not used often.[1] Do the guest bath, the tub nobody showers in, the basement floor drain and the laundry sink, and flush any toilet that rarely gets used. If the smell fades, you found it. The county also says water should be added regularly to seldom-used sinks, toilets and floor drains that may have dried out.[1]
Rule out natural gas first
A rotten-egg smell is not always sewage. If you smell a sulfur or rotten-egg-like odor, you could have a gas leak.[3] Natural gas is naturally colorless and odorless.[3] The utility adds an odorant so you notice it. If you cannot connect the smell to a drain, do not hunt for the source. If you're inside, get out immediately.[3] Then call 911 and your gas utility from outside. Do not use anything that could cause a spark, like a phone, light switch, appliance or flashlight, until you are outside.[3] For the full list of what to do, read what to do if you smell gas in your house.
Other common sources
- The kitchen drain or disposal. Food film in the disposal, the drain pipe or the dishwasher air gap smells like something died. See why a garbage disposal smells.
- A slow leak. A toilet seal that weeps or a drain joint that drips leaves damp material that smells foul. Wet flooring around a toilet is the clue.
- A blocked plumbing vent. If all the traps are full of water and there is still an odor, the problem could be in the vent that carries sewer gas out of the house through the roof.[1] You can often tell because drains gurgle as they empty. The roof is not a place for a homeowner to climb, so this is a plumber's call.
- Water from the tap. If only the hot water smells, the cause may be the water heater, not the drains. See why water smells like rotten eggs.
When the sewer line is the cause
If the traps are full and the smell keeps coming back, think about the line leaving the house. Fairfax County lists frequently clogged drains, odor of sewage, and basement backups during rain as signs that a lateral may require repair.[2] Its code compliance investigators also look for dark colored liquid on the property, soggy ground near the lateral and sewage odors coming from one area of the property.[2] The usual way to confirm a break is a camera inspection by a plumber. More signs are in what are the signs of a broken sewer line.
Stop and call a pro if
- Sewage is coming up through a drain. That is a backup, not an odor. EPA advises calling in a professional with experience cleaning and fixing buildings damaged by sewage or other contaminated water.[4] Read is a sewage backup an emergency and who do I call.
- You smell gas and cannot tie it to a drain. Leave and call 911 and the gas company.
- Every trap is full and the smell persists. The vent or the sewer line needs a plumber with a camera.
- Several drains gurgle or back up at once. That points to a main line problem.
- The floor is soft or stained near a toilet or under a sink. Water is leaking, and the material may need replacing.
- The smell lingers after the source is fixed. Odor can soak into carpet, drywall and insulation, and a restoration company can treat it. Costs are in how much odor removal costs in Virginia, and when to hire an odor removal company covers the decision.
Getting help in Virginia
If it turns out to be plumbing, a licensed plumber can trace it. For more on smells and cleanup, browse restoration answers and the restoration directory. If you want help locating the source, describe the smell and where it is strongest once and licensed local plumbers can quote it.
Common questions
- Why does my bathroom smell like sewage when nothing is wrong with the drain?
- A trap that has dried out is the usual reason, most often in a guest bath, a shower or tub nobody uses, or a floor drain. Fairfax County says sewer gas and odors can enter when fixtures have not been used in a while and the water in the traps has evaporated.[^fairfax-sewer] Run water in the drain for a minute and flush the toilet.
- Is sewer gas dangerous?
- A faint whiff from a dry trap is usually an annoyance, but a strong or lasting sewage smell is a reason to find the source quickly. If you feel unwell while the smell is present, go outside into fresh air, call a plumber, and see a health professional if symptoms continue.
- How can I tell sewage from natural gas?
- Natural gas is naturally colorless and odorless, and the gas company adds an odorant that smells like sulfur or rotten eggs.[^cgv-leaks] The two can be confused. If you cannot tell, or you cannot link the smell to a drain, treat it as gas: if you are inside, get out immediately, then call 911 and the gas company from outside.[^cgv-leaks]
- The smell is only outside. Whose problem is it?
- Fairfax County asks residents who detect a sewer odor outside the home to contact its 24-hour customer line.[^fairfax-sewer] Other utilities handle odor reports for their own mains. Call your local sewer utility, since a main or manhole problem is theirs to fix.
- Can a blocked vent cause a sewage smell?
- Yes. If all the traps are full of water and there is still an odor, the problem could be in the vent that carries sewer gas out of the house through the roof.[^fairfax-sewer] Clearing a roof vent is work at height, so hire a plumber for it.
- Does a sewage smell mean my sewer line is broken?
- It can. Fairfax County lists frequently clogged drains, odor of sewage, and basement backups during rain as signs a house lateral may need repair.[^fairfax-lateral] Rule out dry traps and the kitchen drain first, then have a plumber inspect the line if the smell continues.
Sources
- [1] Wastewater Management: Sanitary Sewer Emergencies, Fairfax County Department of Public Works and Environmental Services. Checked October 28, 2026.
- [2] Sanitary Sewer House Lateral (published November 2024), Fairfax County Department of Code Compliance. Checked October 28, 2026.
- [3] What to do if you smell natural gas, Columbia Gas of Virginia. Checked October 28, 2026.
- [4] Mold Cleanup in Your Home, U.S. Environmental Protection Agency. Checked October 28, 2026.
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