Why Your Kitchen Sink Smells Like Rotten Eggs

Table of Contents

• What Causes the Rotten Egg Smell in a Sink Drain
  • Hydrogen sulfide and sewer gas
  • Dry or dirty P-trap and U-bend
• How to Tell If the Smell Is Coming From the Drain or the Water
  • The two-glass test
  • How to read the results
  • A second check: the drain vs. the overflow
  • What not to do during the test
• Does a Garbage Disposal Smell Like Rotten Eggs?
• How to Clean a Smelly Kitchen Sink Drain Step by Step
  • Before you start: match the method to the cause
  • Step 1: Refill a dry trap first
  • Step 2: Clear the surface and the stopper
  • Step 3: Baking soda and vinegar treatment
  • Step 4: Clean the P-trap
  • Step 5: Clean the garbage disposal
  • Step 6: Clean the overflow opening
  • Step 7: Test and decide
  • Prevention: keep the drain from smelling again
• When to Call a Plumber for a Smelly Sink
• Booking a Drain Inspection With Brass Tacks
• Frequently Asked Questions

Last Updated: October 31, 2026

If your kitchen sink smells like rotten eggs, you are not imagining it. That sulfur odor usually comes from the drain, not the water supply, and it is often caused by something simple like a dry trap or a film of food buildup. At Brass Tacks Plumbing, Heating & Cooling, we help Twin Cities West Metro homeowners sort out these smells every week.

What Causes the Rotten Egg Smell in a Sink Drain

The smell comes from hydrogen sulfide, a gas that forms when bacteria break down organic matter in a drain. Food scraps, grease, soap residue, and slimy biofilm all give those bacteria something to feed on.

The gas usually rises because something is letting it through. Older homes often have aging pipes and venting that cause this, and our guide to plumbing repairs for older homes explains what to check first.

Hydrogen sulfide and sewer gas

Sewer gas is a mix of gases produced in sewer and drain lines, and hydrogen sulfide is the main one that smells like rotten eggs. Your plumbing is designed to keep this gas out, so a sewer smell in the kitchen means the normal seal has failed somewhere.

Common reasons the seal fails:

• A drain that rarely gets used
• A buildup of grease or food in the pipe
• A vent pipe that is blocked or not working right

If the smell is strong, or it shows up in more than one room, call a professional. Sewer gas is not something to ignore.

Dry or dirty P-trap and U-bend

Under your sink is a curved section of pipe called the P-trap, or U-bend. It holds a small amount of water that blocks sewer gas from rising into your kitchen.

Two common trap problems:

• Dry trap: The water has evaporated because the sink has not been used for a while. Vacation homes and guest bathrooms are typical examples.
• Dirty trap: Grease, hair, food, and soap build up on the inside of the trap. This gives bacteria a place to grow and produce the odor.

A dry trap is often the easiest fix. Run water for 30 seconds to refill it. A dirty trap needs cleaning, which is covered below.

How to Tell If the Smell Is Coming From the Drain or the Water

Before you spend time cleaning or call anyone, figure out which system is producing the odor. A sulfur smell from the drain and one from the tap are different problems with different fixes, and guessing wrong wastes time. The test below takes about five minutes and uses items you already have.

The two-glass test

1. Ventilate first. Open a window or run the exhaust fan for a few minutes.
2. Fill a clean glass from the cold tap. Swirl it and sniff right above the rim.
3. Fill a second clean glass from the hot tap. Let the hot water run for 30 seconds first so you are testing water from the water heater, not water that was sitting in the pipe.
4. Compare both glasses to a third glass filled from a different faucet, such as a bathroom or laundry sink.
5. Now smell the drain itself. Lean over the kitchen drain without running water and sniff. Then run the cold tap for 30 seconds and sniff the drain again.

How to read the results

• Cold water smells, hot water smells, and other faucets smell: The issue is likely the water supply or the water heater. A sulfur smell that appears only on the hot side often points to the water heater, especially if it has not been serviced in a while. If a water heater repair specialist confirms the tank is the source, they can flush and inspect it. A smell on both hot and cold at every tap points to the incoming water supply.
• Water smells fine in the glass but the drain smells when you lean over it: The source is the drain, the trap, or the disposal. This is the most common result for a kitchen sink.
• The smell gets stronger after you run water: That points to the drain or trap, because running water disturbs the biofilm and pushes gas up through the opening.

A second check: the drain vs. the overflow

Some kitchen sinks have an overflow opening near the rim. Odor can come from that opening even when the main drain smells fine. Wipe a damp cloth inside the overflow and smell the cloth. If it smells like sulfur, clean the overflow with a bottle brush and hot soapy water.

What not to do during the test

Do not pour bleach or a chemical drain cleaner down the drain before testing. Those products can mask the smell temporarily, make it harder to identify the source, and create dangerous fumes if they mix with other products already in the trap. If you have already used a chemical cleaner, flush the drain with plenty of water and ventilate the room before you continue.

Once you know whether the source is the drain or the water, move to the section that matches your result. Drain odors are covered in the cleaning steps below. Water odors are a water quality or water heater question, and our team can help you sort out which one applies to your home.

Does a Garbage Disposal Smell Like Rotten Eggs?

Yes. A garbage disposal is one of the most common sources of a sink odor. Food scraps can stick to the grinding chamber, the splash guard, and the inside walls. Over time they rot and create the same hydrogen sulfide smell.

To clean the disposal:

• Grind a handful of ice cubes with a little dish soap and cold water.
• Add a few lemon or orange peels and grind again to freshen things up.
• Wipe the splash guard and the underside of the rubber flange with a damp cloth.

If the smell stays after cleaning, the problem may be deeper in the drain or the trap, and the steps below will help.

How to Clean a Smelly Kitchen Sink Drain Step by Step

This routine takes about 30 to 45 minutes and works for most kitchen sink odors that come from the drain. For a deeper look at the methods involved, see our guide to clearing a plumbing drain clog. You will need baking soda, white vinegar, hot water, a bucket, a bottle brush, a plunger, and gloves.

Before you start: match the method to the cause

Use the result from the drain-versus-water test to pick your starting point.

• Smell only after the sink has sat unused: Start with Step 1 and Step 2. A dry trap is often the whole problem.
• Smell every time you run water: Start with Step 2 and Step 4. Biofilm in the trap or drain is the likely source.
• Smell only when the disposal runs: Start with Step 5.

Step 1: Refill a dry trap first

If the sink has not been used in a while, run the cold tap for a full minute. That refills the P-trap and restores the water seal. Sniff the drain after a few minutes. If the smell is gone, you are finished. If it comes back, continue to Step 2.

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Step 2: Clear the surface and the stopper

Pull out the stopper or strainer and clean it with hot soapy water. Remove visible debris from the drain opening with a gloved hand or tweezers. Wipe the inside of the drain opening with a damp cloth and smell the cloth. If the cloth smells like sulfur, the buildup is close to the surface and the next step will help.

Step 3: Baking soda and vinegar treatment

Pour about half a cup of baking soda down the drain, then half a cup of white vinegar. The mixture will fizz, which helps loosen grime on the pipe walls.

This treatment is safe for most pipes, but do not combine it with a chemical drain cleaner. Mixing vinegar with bleach or a commercial drain cleaner can create dangerous fumes.

Step 4: Clean the P-trap

Place a bucket under the trap. Loosen the slip nuts by hand, then remove the trap. Empty the contents into the bucket and scrub the inside with a bottle brush and hot soapy water. Rinse it well. Reinstall the trap, making sure the washers sit properly, and tighten the nuts snugly by hand. Avoid overtightening, which can crack plastic fittings.

Step 5: Clean the garbage disposal

Grind a handful of ice cubes with a little dish soap and cold water. Then add a few lemon or orange peels and grind again. Wipe the splash guard and the underside of the rubber flange with a damp cloth, because food residue often collects there. Run cold water while the disposal runs, and keep it running for a few seconds after the grinding stops.

Step 6: Clean the overflow opening

If your sink has an overflow opening near the rim, use a bottle brush and hot soapy water to scrub inside it. Odor can come from that opening even when the main drain is clean.

Step 7: Test and decide

Run water for a minute and sniff the drain. If the smell is gone, you are finished. If it lingers, or if it returns within a few days, the cause is likely a blocked vent, a failing trap seal, or a sewer line issue. Those problems need a professional inspection, and the next section explains the signs.

Prevention: keep the drain from smelling again

A few habits reduce repeat odors. Run cold water for 15 to 30 seconds after each use of the disposal. Avoid pouring grease or cooking oil down the drain. Once a month, run the baking soda and vinegar treatment as a maintenance step.

Here is a quick reference for the cleaning steps and the cause each one targets.

When to Call a Plumber for a Smelly Sink

Some sink smells clear up with basic cleaning. For stubborn buildup that resists it, hydro jetting uses high-pressure water to scour the pipe walls. If the odor keeps coming back, kitchen and sink drain cleaning in the Plymouth and West Metro area can clear the buildup that basic steps miss. Others point to a bigger issue that needs a licensed plumber. Call a professional if:

• The smell returns within a few days of cleaning.
• Several drains in the house smell like sewer gas.
• Water drains slowly or gurgles when other fixtures are used.

A plumber can run a camera through the drain line to find the cause and check the vent. For drain or sewer problems that cannot wait, emergency plumbing support is available.

Watch out: Do not ignore a sewer smell that is strong or comes with slow drains, gurgling toilets, or wet spots on the floor.

Booking a Drain Inspection With Brass Tacks

If the smell will not go away after cleaning, or if you suspect something deeper in the system, our team at Brass Tacks Plumbing, Heating & Cooling can take a look.

Our kitchen and sink drain cleaning service is a good place to start for simple clogs and buildup. For older homes with more complicated drain or sewer issues, we will explain what we find and what your options are before any work begins.

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