Sewer odors
Sewer Smell in the House or Yard: What It Means
Short answer: a sewer smell usually points to a dry drain trap, a blocked or leaking line or a missing cleanout cap. A strong rotten-egg smell can also be natural gas, so treat that as an emergency first. If the smell stays after you fix the simple causes, get the line checked.
Quick checks
- Run water in rarely used drains
- Check that the cleanout cap is on
- Look for slow drains or gurgling
- If the smell is strong, ventilate and call
A rotten-egg smell can be gas. Leave and call your gas company or 911.
First, rule out a gas leak
Natural gas is given a rotten-egg smell on purpose. If the smell is strong, or you hear hissing, leave the building and call your gas company’s emergency line or 911 from outside. Do not light anything or use switches.
If it is a sewer smell instead, it is usually more of a musty, sulfur-like odor near drains.
Last updated October 2026.
Common causes of a sewer smell
| Cause | Where you notice it | What helps |
|---|---|---|
| Dry drain trap | Rarely used sink, tub or floor drain | Run water for a minute to refill the trap |
| Missing or loose cleanout cap | Yard, near the house wall | Replace or tighten the cap |
| Partial blockage in the line | Several drains, gurgling, slow flow | Get the line cleaned and filmed |
| Damaged or cracked line | Wet spots or odor in the yard | Camera inspection to find the break |
| Vent problem | Odor in bathrooms or on the roof | Plumber check of the vent |
What to do
- Run water in every drain, especially ones you rarely use.
- Check the yard for a loose cleanout cap or a wet, soggy patch.
- Notice whether any drains are slow or gurgling.
- If the smell remains, call for a camera inspection.
See signs of a clogged sewer line and sewer camera inspection.
When to call right away
- Sewage is coming up in a drain or the yard
- The smell is strong and does not go away after running water
- You also have slow drains in more than one fixture
Stop using water and see emergency sewer backup.
Where a sewer smell usually comes from
A plumbing manufacturer lists the most common sources. Most are simple and cheap to fix (Oatey).
| Source | What happens | What helps |
|---|---|---|
| Dry drain trap | The water seal evaporates in a drain that is rarely used, often a floor or laundry drain | Run water down it. About a gallon a month keeps the seal |
| Blocked or broken sewer line | Gas is pushed back into the house | Camera and cleaning or repair |
| Toilet seal | A failed wax ring or low flange lets gas escape at the base | Reseal or reset the toilet |
| Blocked vent | Gas cannot leave through the roof and traps can be pulled dry | Clear the vent |
| Water heater | Sulfur bacteria can make a rotten-egg smell at hot taps only | Flush or service the heater |
| Dirty overflow drain | Buildup in a sink or tub overflow | Clean it |
Simple checks you can do first
- Find which room the smell is in, and which drain is closest.
- Run water in every drain in that room, including floor drains, for a minute.
- Check whether the smell is only at hot water taps. That points to the water heater.
- Look at the base of the toilet for movement or staining.
- Open windows and run exhaust fans while you check.
Air fresheners only cover the smell. Find the source.
Is sewer gas dangerous?
Sewer gas can contain hydrogen sulfide, methane and ammonia. At high levels it can be dangerous. Headaches, nausea, dizziness and irritated breathing are listed as symptoms. If several people in the home feel unwell, leave and call a plumber right away (Oatey).
A rotten-egg smell is not the same as natural gas. If you smell the gas used for cooking and heating, leave the house and call the gas company or 911.
Reporting a sewer odor to the city
In the City of Los Angeles, LA Sanitation takes odor reports through an online form. A crew is sent, and a representative follows up. Between 12:30 a.m. and 6 a.m. the page says to call the 24-hour Customer Care Center at 1-800-773-2489. If the smell is outside and affects the street, report it. If it is inside your home, check your own drains first. See who is responsible.
Common questions
Why does my bathroom smell like sewer?
Most often a dry trap in a rarely used drain. Running water for a minute usually fixes it. If not, check the line.
Is sewer gas dangerous?
Strong or lasting sewer gas can be harmful, so ventilate and do not ignore it. Natural gas is a different, more urgent problem.
Will hydro jetting remove the smell?
If buildup in the line is the cause, cleaning often helps. A camera shows whether there is a crack or leak.
Smell will not go away?
Call and tell us what you notice, and a local plumber will talk you through the next step.