An infrequently used drain may have a dry trap
A localized odor at a seldom-used sink, shower, tub, or floor drain may occur when the trap’s water seal evaporates. One brief water refill is a reasonable check when there is no backup, leak, or strong unexplained gas odor.
Why this result fits
- The odor is strongest at one drain.
- The fixture has not been used recently.
- Adding water may restore the trap seal and reduce the odor.
What to do now
Screen for plumbing warnings
Do not test if the drain is backing up, leaking, gurgling with other fixtures, or producing a strong widespread sewer or gas-like odor.
Refill the trap once
Run the fixture briefly, or add plain water to an accessible floor drain, without removing covers or opening plumbing.
Observe and report
If the odor does not clearly improve, returns quickly, or affects multiple drains, stop troubleshooting and contact maintenance.
Stop and escalate if
- The odor is strong, widespread, gas-like, or causes irritation, dizziness, nausea, or breathing difficulty.
- There is sewage, a backup, gurgling across fixtures, or visible plumbing damage.
- Water does not drain normally or appears elsewhere.
What not to do
- Do not add bleach, drain cleaner, fragrance, mineral oil, or another chemical.
- Do not open the trap, drain cover, cleanout, or plumbing vent.
- Do not assume every sewer-like odor is a harmless dry trap.
Message you can send to maintenance
The odor is strongest at the infrequently used [fixture/drain]. I added plain water once, and the odor [did not improve/returned after time]. There is [no backup or gurgling / describe symptoms]. Please inspect the trap, drain, and venting.
Help prevent a repeat
- Run water periodically in seldom-used fixtures when building guidance permits.
- Report odors that persist, recur quickly, or involve multiple drains.
If this does not match
Sources and review date
- Controlling Pollutants and Sources: Drain Traps — U.S. Environmental Protection Agency
Content last reviewed: under the Apartmentwise methodology.