Why Does My Sink Smell Bad? (and How to Get Rid of Odors)

A bad smell coming from a kitchen or bathroom sink is one of the most common plumbing complaints, and most of the time it’s something you can fix yourself in under an hour. The type of smell is a strong clue. A sour or musty odor usually points to buildup in the drain, while a sewer smell suggests a problem with the trap or venting. This guide explains what each smell means, how to clean each part of the sink, and when an odor is a sign of something a plumber should look at.

General information only. Electrical, gas, and refrigerant work can be dangerous and in many states requires a licensed contractor. When in doubt, call a licensed pro.

What the Smell Is Telling You

Sour, musty, or rotting smell: Usually food, grease, soap scum, hair, or biofilm decaying in the drain, the P-trap, the overflow, or a garbage disposal.
Sewer smell: Sewer gas is getting past the P-trap. The trap may be dry, leaking, or loose, or a vent problem may be pulling water out of the trap.
Rotten eggs only when the hot water runs: This often comes from the water heater, not the drain. Bacteria in the water can react with the tank’s anode rod and produce a sulfur smell. Fill a glass with hot water, step away from the sink, and smell it. If the water itself smells, the drain isn’t the cause.
Rotten eggs that don’t go away, or that are strongest near a gas appliance: Natural gas has an added odor that smells like rotten eggs. If you suspect a gas leak, leave the house and call your gas utility from outside.

Common Causes of a Smelly Sink

A dry P-trap

The U-shaped pipe under the sink, called the P-trap, holds a small amount of water that blocks sewer gas from coming up the drain. In a guest bathroom or any sink that isn’t used for weeks, that water can evaporate and let odors through.

Buildup in the drain and trap

Grease, food, toothpaste, soap scum, and hair stick to the inside of the drain and trap. Bacteria feed on it and form a slimy biofilm that smells sour.

Bathroom pop-up stoppers and overflows

The pop-up stopper in many bathroom sinks collects hair and gunk. The overflow hole near the rim leads to a channel that rarely gets rinsed, so it can grow mold and bacteria.

Garbage disposal residue

Food can collect under the rubber splash guard, on the grinding chamber walls, and in the drain line below a disposal.

Dishwasher connection

On many kitchen sinks, the dishwasher drains into the disposal or sink drain. A dirty dishwasher filter, a drain hose without a proper high loop or air gap, or a clogged air gap can send dirty water back toward the sink and cause odors.

Loose, cracked, or missing parts

A loose slip nut, a cracked trap, or a worn washer can let sewer gas escape even when the trap is full. Some older or improperly modified sinks have an S-trap or no proper trap, which can siphon dry.

Venting problems

Drains need air from a vent to flow smoothly. If a roof vent is blocked by debris or nests, or a mechanical vent under the sink (an air admittance valve) fails, draining water can pull the trap dry. Gurgling sounds and slow drains are common signs.

Step-by-Step: How to Get Rid of Sink Odors

Run water to refill the trap. For a sink that hasn’t been used in a while, run water for 15 to 30 seconds. If the smell goes away and stays away, a dry trap was the problem.
Clean the stopper and drain opening. In a bathroom sink, loosen the pivot nut behind the drain pipe under the sink, pull out the stopper, clean off the hair and buildup, and reinstall it. A plastic drain-cleaning strip (a barbed “zip” tool) pulls hair from the top of the drain.
Clean the overflow. Scrub the overflow opening with a small bottle brush and a mild cleaner or a dish soap and hot water solution, then rinse it by pouring water into the overflow.
Clean the P-trap. Put a bucket underneath, loosen the slip nuts by hand or with pliers, and remove the trap. Wash it out with a brush and hot, soapy water, check the washers for wear, and reinstall it. Tighten the nuts snugly by hand plus a little more, then run water and check for drips.
Flush the drain. Pour about half a cup of baking soda into the drain, follow it with about a cup of white vinegar, wait 15 minutes, and flush with plenty of hot tap water. This is a mild cleaner that helps loosen light buildup. It won’t clear a real clog. Hot tap water is safer than repeatedly pouring boiling water into plastic drain pipes.
Try an enzyme drain cleaner for biofilm. Enzyme or bacterial drain treatments digest organic buildup over several hours, and are often best used overnight. Follow the label.
Deodorize the disposal. Turn off the disposal at its switch, and at the breaker if you will reach inside. Lift the splash guard and scrub its underside with a brush and dish soap. Then, with cold water running, grind a handful of ice cubes and a little coarse salt, followed by a few citrus peels. Never put your hand inside the disposal.
Check the dishwasher. Clean the dishwasher’s filter and confirm the drain hose rises in a high loop under the counter or connects to an air gap at the sink.

Safety Notes

Never mix cleaners. Mixing bleach with vinegar, ammonia, or other drain products can release toxic gases.
Be careful with chemical drain openers. Caustic drain openers can damage some pipes and are dangerous if they splash back when you open the trap. Avoid them, and tell a plumber if you’ve already used one.
Wear gloves and eye protection when opening a trap. The water inside is dirty.

When to Call a Plumber

The smell comes back after you’ve cleaned the trap, stopper, overflow, and disposal.
Several drains smell, gurgle, or drain slowly at the same time.
You notice a sewer smell elsewhere in the house, or water backs up into a tub or floor drain.
The trap leaks after you reinstall it, or the drain parts are cracked or corroded.
You suspect a venting problem, a missing or incorrect trap, or a failed air admittance valve.
The sulfur smell is in your hot water. A plumber can check the water heater and may suggest a different anode rod.

DIY vs. Professional: A Quick Guide

Refilling a trap, cleaning stoppers and overflows, removing and cleaning a P-trap, deodorizing a disposal, and cleaning a dishwasher filter are all beginner-friendly jobs. Replacing a plastic trap kit is usually DIY-friendly too. Clearing a roof vent involves working on the roof and is often better left to a pro. Sewer line problems, correcting an S-trap or improper venting, and water heater anode work are generally jobs for a licensed plumber.

Prevent Sink Odors Before They Start

Run water in guest bathrooms and other rarely used sinks at least once a week.
Use a sink strainer and keep grease and food scraps out of the drain.
Run hot water for a few seconds after washing greasy dishes.
Clean bathroom stoppers and overflows every month or two.
Clean under the disposal splash guard regularly and run the disposal with plenty of cold water.
Clean the dishwasher filter according to the manufacturer’s instructions.

If your air conditioner or vents smell instead of the sink, see our guide on why an AC smells bad.

Frequently Asked Questions

Why does my sink smell bad?

Most sink odors come from buildup of food, grease, soap, or hair in the drain, trap, overflow, or disposal. Sewer smells usually mean the P-trap is dry, loose, or leaking, or there is a vent problem.

Why does my bathroom sink smell like sewer?

The trap may have dried out from lack of use, the slip nuts may be loose, or the overflow and stopper may be full of buildup. Run water to refill the trap and clean the stopper and overflow. If the smell persists, have a plumber check the trap and venting.

Does baking soda and vinegar really work on sink smells?

It’s a mild cleaner that can help with light buildup and freshen a drain, especially followed by plenty of hot water. For heavier buildup, removing and cleaning the trap or using an enzyme cleaner works better.

How can I prevent sink odors?

Use the sink regularly so the trap stays full, keep grease and food scraps out of the drain, clean stoppers and overflows every month or two, and keep the disposal clean.