Short answer
Run water for a minute in case the trap has dried out. If the smell stays, pull and scrub the stopper, then brush out the overflow channel and clean the P-trap. Use an enzyme drain cleaner for upkeep. If the smell is like sewage, comes from several drains, or returns within days, call a licensed plumber to check the vent and the line.
Four causes of a smelly sink drain
| Cause | Clues | Fix |
|---|---|---|
| Biofilm in the drain | Rotten egg smell right at the drain; slimy stopper | Pull and scrub the stopper, clean the trap |
| Dry P-trap | Sewer smell from a sink nobody uses | Run water for a minute |
| Dirty overflow | Smell is strongest at the overflow hole near the rim | Brush and flush the overflow channel |
| Venting problem | Gurgling, traps that keep drying out, smell at several drains | Call a licensed plumber |
Mr. Rooter Plumbing lists the same causes for a rotten egg smell: bacteria in the drain producing hydrogen sulfide, a dried-out trap, and venting problems.
Biofilm: the usual culprit
Hair, soap, toothpaste and skin cells coat the stopper and the pipe walls. Bacteria live in that slime and give off hydrogen sulfide, the gas that smells like rotten eggs. The stopper and the pivot rod collect the most, which is why the smell is often worst right at the drain.
A dry trap
The P-trap holds a few inches of water that blocks sewer gas. The International Plumbing Code calls for a seal of at least 2 inches (ICC). In a guest bath or a basement sink that goes weeks without use, the water evaporates and the gas comes straight up. Running water for a minute fixes it.
The overflow channel
Most bathroom sinks have an overflow hole near the rim. Behind it, a channel runs down inside the sink to the drain. Water rarely flows through it, so slime builds up and stays damp, and it smells. People clean the drain and miss this entirely.
Venting
Every drain has a vent pipe that lets air in so water flows smoothly and traps keep their water. If the vent is blocked, draining water can siphon a trap dry, and sewer gas gets in. Gurgling and slow drains often come with it; see how to fix a slow sink drain.
How to get rid of a sink drain smell
What you need
Run water to refill the trap
Run the tap for a minute. If the sink has not been used in a while, this alone may fix it. Check again in an hour.
Pull and scrub the stopper
Lift or twist the stopper out. If it is held by the pivot rod, loosen the pivot nut under the sink and pull the rod back so it comes free. How to remove a sink stopper shows each type. Scrub off the slime with hot soapy water and a brush, and wipe down the pivot rod.
Scrub the drain opening
With the stopper out, run a bottle brush down the drain as far as it reaches and work it around. Flush with hot tap water.
Clean the overflow channel
Push a small bottle brush into the overflow hole and scrub as far in as it goes. Then pour a pitcher of hot tap water slowly into the overflow to rinse the channel.
Clean the P-trap
Set a bucket under the trap, unscrew both slip nuts, and empty it. Scrub the inside, check the slip washers, and refit it snugly. Run water to refill it and check for drips.
Use an enzyme cleaner for upkeep
Once the drain is clean, an enzyme drain cleaner can help keep slime from building back up. Follow the label for amount and timing, and do not combine it with any other drain product.
For a sink you rarely use
A guest bathroom or basement sink needs water now and then to keep its trap full. Run it for a minute every week or two. If the trap dries out within days rather than weeks, that can be a venting issue, so ask a plumber.
When to call a plumber
- The smell is sewage rather than rotten eggs, and it fills the room.
- Several drains smell, or the smell comes from the floor or wall rather than the sink.
- Drains gurgle, or traps dry out within days.
- The smell is back within days of a full clean.
Those point to a vent, a cracked pipe, a missing trap or a problem in the main line, which a licensed plumber should track down.
Keep it from coming back
Pull and rinse the stopper every few weeks, brush the overflow when you clean the sink, and use a hair catcher so less ends up in the drain. The sink drain strainer guide lists options. A baking soda and hot water rinse is fine as gentle upkeep, but a brush does more.
Questions people ask
Why does my bathroom sink smell like rotten eggs?
Usually bacteria in the slime (biofilm) on the stopper, the pipe walls and the overflow channel, which give off hydrogen sulfide. Cleaning the stopper, the overflow and the trap removes most of it.
Why does a sink I rarely use smell like sewer gas?
The water in the P-trap evaporates over time. Once the trap is dry, nothing blocks sewer gas from coming up the drain. Run water for a minute to refill it.
Can I pour bleach down a smelly sink drain?
It is not needed, and bleach can release toxic gas if it meets another cleaner or an acid. Scrubbing the stopper and overflow and cleaning the trap removes the slime directly. Never mix drain products.
Why does my sink smell even after cleaning?
Check the overflow channel, which is easy to miss, and the trap. If both are clean and the smell continues, or you hear gurgling, the vent may be blocked or the trap may be getting siphoned dry. That needs a plumber.
Do enzyme drain cleaners work for smells?
They are made to break down organic buildup slowly and are a reasonable upkeep step after you have cleaned the drain by hand. Follow the label for how much to use and how long to leave it.
Sources
Last reviewed October 12, 2026. Parts, sizes and listings change; check the product details before you buy, and follow the maker’s instructions.