Quick Answer:
If you smell something coming from the sink’s overflow while washing your hands, it’s usually trapped soap scum, bacteria, or stagnant water in the overflow channel. Start by scrubbing the overflow opening with a small bottle brush and warm soapy water, then flush the channel by filling the bowl a little and letting water run into the overflow for about 30 seconds. Repeat those steps until the odor fades.
Why This Happens
The overflow channel is a narrow, often damp passage that connects the bowl to the drain. It catches splashes and can hold a thin film of water, soap residue, and skin oils. Over time that film becomes a place for bacteria and mildew to grow, which produces a noticeable odor when disturbed. Poor airflow inside the channel slows drying and lets smells linger.
Step-by-Step What to Do
1. Get ready
- Wear disposable gloves and have a small bottle brush, dish soap, and a cup or container to pour water from.
- Turn on the bathroom fan or open a window for ventilation.
2. Scrub the overflow opening
- Dip the small bottle brush in warm, soapy water and insert it into the overflow opening. Move it back and forth to loosen grime and film.
- Work around the ring of the opening and try to reach as far into the channel as the brush will go. Wipe away loosened material on a paper towel.
3. Flush the overflow
- Fill the sink bowl slightly (not to the top) so water can reach the overflow inlet, then let water run into the overflow for about 30 seconds. This pushes loosened debris down the channel and toward the drain.
- Empty the bowl and check for smell. If it persists, repeat the scrub-and-flush cycle until the odor fades.
4. Final checks
- Run water through the main drain for a minute to clear remaining debris.
- If available, use a flashlight to look into the overflow opening; repeat cleaning if you still see film.
What Not to Do
- Don’t pour bleach directly into the overflow opening—trapped fumes can linger and it may not remove sludge deep in the channel.
- Don’t force rigid wires or sharp objects down the overflow; you can damage the channel or the drain connection.
- If the overflow won’t flush or smells strongly despite repeated cleaning, avoid more DIY chemical pours—professional cleaning may help.
When to Call a Professional
Call a plumber if:
- The smell persists after several scrub-and-flush attempts.
- You cannot flush the overflow because of a blockage or trapped debris.
- There is visible mold growth inside the channel or repeated odors despite cleaning, which could indicate deeper buildup or a venting issue.
Safety Notes
- Work in a well-ventilated area and avoid mixing cleaners. Warm soapy water is usually enough for this routine cleaning.
- Wear gloves to protect your skin from grime and any cleaning agents you choose to use.
- If you use a commercial cleaner, follow the label directions and avoid pouring strong bleach into confined channels where fumes can concentrate.
Common Homeowner Questions
- Smell after dishwasher drain — The dishwasher can send odors into nearby drains; check and flush the trap if odors spread.
- Food odor after city outage — Spoiled food can make your sink area smell; clear and clean any affected items and then clean the overflow channel.
- How long before the smell is gone? — After a proper scrub and a few flush cycles most odors fade within one cleaning session; persistent smells may need a pro.