A sewer smell with no backup. Usually a dry trap. Try the free fix first.
Sewer gas is unpleasant and, in high concentrations, harmful. A dry trap is fixed in one minute with a jug of water. A broken vent or wax ring takes a plumber this week.
What is probably happening
- A trap has dried out. Oatey: a floor drain, a basement shower, a guest bath or a laundry sink that goes unused for two to four weeks loses its water seal and lets sewer gas in.
- The wax ring under a toilet has failed, so gas escapes at the floor. A toilet that rocks is the giveaway.
- A plumbing vent on the roof is blocked, or a vent pipe in the attic is disconnected.
Do this in the next five minutes
- Pour a gallon of water down every drain you rarely use: floor drains, spare showers, laundry tubs. Oatey's fix is a gallon a month.
- Add a tablespoon of cooking oil after the water in a floor drain to slow evaporation.
- Push each toilet gently. If one rocks or the floor around it is soft, that is the wax ring.
- Open windows and give it a day. If the smell is gone, it was a trap.
Do not
- Do not mask it with air freshener and forget it. Sewer gas contains hydrogen sulfide and methane.
- Do not pay an emergency call for a smell with no backup.
- Do not accept a camera and jetting quote until the traps and the wax ring have been checked.
Who to call
A licensed plumber
If the water trick fails, a plumber does a smoke test to find a bad vent or a failed wax ring, which no other trade does.
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What it should cost
$150 to $391, averaging $271
Toilet repair national range, which covers pulling and resetting a toilet with a new wax ring. A smoke test or vent repair is quoted separately
Source: Angi, toilet repair cost, updated July 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the plumbing page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Will you do a smoke test, and what does it cost?
- Did you check every trap and the wax rings before recommending anything bigger?
- If it is a vent, where is the break and how will you reach it?
- Is the trip fee applied to the repair?
End the call if
- A main line replacement recommended for a smell with no backup and no camera.
- No smoke test offered when the trap fix failed.
- An emergency premium.