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Why Does Bathroom Sink Smell Like Rotten Eggs Or Sewer?

While using your bathroom sink, suddenly you might feel to throw up because of a disgusting smell like rotten eggs or sewer that is coming from the bathroom sink.

In this situation, if you don’t know what is the source of such an awful smell, you certainly would want to know why does your bathroom sink smell like rotten eggs or sewers.

Therefore, to get rid of the smelly bathroom sink, let’s learn the reasons behind it.

Why Does The Bathroom Sink Smell Like Sewer?

The bathroom sink smells like sewer due to blocked vents in the drain. If the vents are clogged, while flushing the toilet it’ll create enough vacuum to grovel up P-trap’s water and release sewer gas through the sink. Damaged or deteriorated sewer pipes or main drains can cause a sewer smell too.

Generally, the foul sewer smell coming out from your bathroom sink is caused if there are blocked ducts in the drain that is connected to the sink’s P-trap.

Because something is clogging up the vents, whenever somebody will flush the toilet in the same bathroom, a sufficient vacuum will be created there to suck the P-trap’s water.

Therefore, sewer gas will fill up that area, and while using the sink, sewer gas will get releases into the air.

Sometimes, if the sewer pipes get damaged underground or the main drain has gotten deteriorated, the bathroom sink can smell like a sewer.

What Causes A Bathroom Sink To Smell Like Sewer?

Here the main causes behind your bathroom sink smelling like sewer have been explained.

Poorly Functioning P-Trap:

A well-functioning P-trap holds some water that stops sewer gas to get released into the bathroom through the bathroom sink or sink drain.

If the P-trap is not functioning appropriately or the water in the P-trap got evaporated (a dried P-trap), sewer gases get enough space to get released through the bathroom sink. Therefore, it makes the bathroom sink stinky.

Clogged Vents:

When the vents in the drain are clogged up, back-flowing sewer gases make their way to get released in the bathroom through the sink’s P-trap. As a result, the gas gets into the air by the sink and makes it smelly with sewer gas.

Sink Odor:

Sometimes it’s the sink itself that smells like sewer. The bathroom sinks have an overflow flow hole that allows quick drainage. If the sink isn’t used often, mildew and dirt build-up and cause an unpleasant sewer smell in the sink.

How To Get Rid Of The Sewer Smell In The Sink?

3 simple ways of getting rid of the sewer smell in the sink are described here.

Hot Water, Baking Soda, Vinegar:

If the sink itself is the sole problem, use hot water, vinegar, and baking soda to clear out the dirt and mildew. First, pour half a cup of baking soda and let it rest for 15 minutes. Then pour half a cup of white vinegar and let it rest for 15 minutes also.

Lastly, pour boiling hot water to move a dirt/mildew.

Clear Out Vents:

When there is a blockage in the vents of the drain, clear the obstacles will solve the problem. By using a suction pump you can remove the blocking objects from the vents. And then wash it with hot water to clean the vents in the drain properly.

Clean And Refill P-Trap:

Since evaporated water in the P-trap makes it dry and mold/bacteria can grow there, so if it’s the reason behind the sewer smell, you must clean the P-trap. Just open the P-trap and clean it thoroughly with a wire brush. And wash it with hot water.

After that refill the P-trap with some water until it reaches its optimal level.

Why Does The Bathroom Sink Smell Like Rotten Eggs?

Bacterial activities take place in the drain or sewage of an unused/dirty bathroom sink that generates hydrogen sulfide gas and causes a smell like rotten eggs in the bathroom sink. Besides, polluted water, clogged vents, or dried P-traps also can make the bathroom sink smell like rotten eggs.

When a bathroom sink is not used frequently or is dirt has piled up inside the pipes, drain, or sewage, their bacteria produce a gas called hydrogen sulfide. And it comes up from the sewer or the drain. As a result, the bathroom sink smells like rotten eggs.

Sometimes bathroom vents can get clogged because of lodged stray hairs which also can cause a rotten smell in the sink.

And lastly, P-traps of the bathroom sink can get dried up if the sink is not used at all. Therefore, hydrogen sulfide gas gets generated there and makes the bathroom sink odorous with the rotten egg-like odor.

What Causes A Bathroom Sink To Smell Like Rotten Eggs?

Smell like rotten eggs comes from several potential sources and causes a styling bathroom sink. If you are encountering such a stinking bathroom sink at your home, go through this section and learn the detailed explanations regarding all possible causes.

Hydrogen Sulfide Gas:

The formation of hydrogen sulfide gas due to bacterial activities is the major reason that causes bad smells like rotten eggs in the bathroom sink.

It usually happens if the bathroom sink’s pipes, drain, or sewage is dirty. As piled up dirt will block the way for water or other things to be flushed down, so bacteria will build up in such a dirty and humid spot.

And gradually they will flourish and create hydrogen sulfide gas there and will make the bathroom sink stink like rotten eggs.

Dried P-trap:

A dried P-trap is another possible source of rotten egg-like smell coming out from the bathroom sink.

The P-trap, it has some water inside the pipe that blocks the hydrogen sulfide gas in the pipes from going up.

So when the bathroom sink is not used for a long time the water in the pipe gets vaporized. And leaves sediments that gradually settle down in the pipe and create hydrogen sulfide gas that smells like rotten eggs and makes the bathroom sink smelly.

Clogged Vents/Pipes:

Clogged vents are also a reason that causes the bathroom sink to smell like rotten eggs. As stray hairs lodged in soap foam can clog the pipe of the bathroom sink. 

And at a point, the vents will be fully clogged and will create a bad smell like rotten eggs because other flushed things will also get stuck with the matted hair.

What Does It Mean When Your Sink Smell Like Rotten Eggs?

When your sink smells like rotten eggs, in the first place it will indicate that perhaps the water is being contaminated due to sulfur bacterial activities in the water tank.

However, a rotten egg-like smelly sink also can mean that the sink’s overflow hole is contaminated because of outgassing. Or bacteria are developing at the edges of the overflow hole. It can also indicate a clogged/dried P-trap or U-bend as well.

How To Get Rid Of The Rotten Egg Smell In The Bathroom Sink?

To help you out with getting rid of such horrible smells like rotten eggs from your bathroom sink, here the ways of stopping this smell are described below.

Spray Clorox Into The Overflow Hole:

Clorox bleach is an active element that is an expert in destroying bacteria because it has hypochlorous acid.

So if the rotten egg-like smell is coming because bacteria are producing hydrogen sulfide gas, use Clorox bleach. Just fill up a sturdy spray bottle with Clorox bleach and spray plenty tons of bleach into the bathroom sink’s overflow hole.

And wait a day or two days for the bacteria to be terminated and the egg smell to be stopped.

Unblock The Vents:

Unblock clogged vents to get rid of the stinky rotten egg smell.

For that, take a suction pump and plunge down the sink’s drain until it removes all blockages. And then pour some boiling hot water into the drain to flush out any staying congealed build-up. And after 5 minutes pour cold water.

Check The P-Trap:

As dirty/dry P-trap can also cause a rotten egg-like smell, check and clear out the P-trap. Just use a wrench to remove the P-trap and desolate any holding water. If it’s dirty, clean the trap with a wire brush and flush it out with warm water to clean any residues.

Then it should stop smelling like rotten eggs.

Why Does My Bathroom Sink Drain Smell Like This:

Your bathroom sink may not only smell like rotten eggs. You can smell some other kind of awful smell coming from your bathroom sink. The reasons behind those smells are explained in brief below.


Your bathroom sink drain can smell like fish despite the absence of any trace of fish in that spot due to sewage gas leakage.

If the fishy smell is not caused by sewage gas, either it can be contaminated water or an electrical fault that is causing an unpleasant fishy smell.


A bathroom sink drain can smell like urine if the toilet seat in the same bathroom is faulty or has a mold problem. Otherwise, improper installation of the toilet seat or usual tear wear and tear also can make the bathroom sink drain smells like urine.


Needless to mention that mildew thrives the best in dark and humid spots and the sink pipes are the best place for them to flourish. As a result, mildew spores grow up and spread. And later on, releases a foul fishy smell through the bathroom sink drain.


If the bathroom sink drain is blocked with stray hair, repressed oil, and starches, gradually it will build up an ideal spot for mold to have a feast day.

Therefore, anything that is pathogen like bacteria or molds will get all available organic things in the drain such as darkness, moisture, and organic matters to live. And they will produce this dirt-like smell in the bathroom.


A foul poopy smell coming from your bathroom sink drain is caused by drain obstruction. When the drain is clogged, it will create a blockage for flushed water to flow voluntarily through the sink pipes.

And when the water will not be flushed properly, it will get stuck with the solid things inside the clogged drain.

As a result, those materials will start decomposing and will create a poopy smell in the bathroom sink drain.


The skunk smell comes from the bathroom sink drain because of natural gas. The skunk smell is basically a chemical named mercaptan which indicates a warning about the leaking natural gas threat.


Your bathroom sink drain can smell like septic if bacteria is being fed on the detritus inside the pipes. As it will give hydrogen sulfide gas which creates a septic smell and the septic smell is similar to a foul-smelling rotten egg-like smell.

Besides, if mold goes on the debris inside the pipe, it can also cause a septic smell that will come out from your bathroom’s sink drain.


The sulfur smell that comes from your bathroom sink drain is caused by bacterial activities that have been taking place in the sewage or pipes attached to the basin sink. It happens when the sewage is dirty or the pipes are dried inside.

As dirt and humidity inside the sewage is an ideal habitat for bacteria to produce hydrogen sulfide gas that smells like sulfur/rotten eggs.

Why Does My Bathroom Sink Smell When Water Runs?

Awfully stinking bathroom sink, while water is running through the sink tap, is caused when something inside the fixture is decomposing.

Sometimes, the bathroom sink’s overflow hole gathers bacteria and dirt. And gradually bacteria build up and organic matters start to decompose.

Therefore, a foul odor is produced, and when the water starts to flow down and comes into contact with air, the air is whacked back by overflow and odor comes out with it. And at that time, though the drain is not faulty, the bathroom sink smells when water runs.

Why Does The Bathroom Sink Water Smells?

The main reason behind the bathroom sink water smell is growing bacterial in the drain. As time passes by, organic matters start to gather up on the drain’s wall and become food for bacteria to live well there.

And these bacteria produce sulfur gas that smells like sewage/rotten eggs and makes the bathroom sink water smelly.

How Can I Make My Bathroom Sink Smell Better?

You can make your bathroom sink smell better just by using baking soda, white vinegar, and boiling hot water.

First, put ½ cup of baking soda in the duct and allow it to rest for at least 15 minutes. Then pour half a cup of white vinegar on top of the baking soda and let it rest for 15 minutes more. After that pour boiling hot water into the drain and clean it.

And then again pour ½ cup baking side and a few drops of essential oil, allow it to rest and wash out with hot water again. It will make your bathroom sink smell fresh.

Final Thoughts:

Basically, the bathroom sink smells like rotten eggs or sewer due to hydrogen sulfur gas produced by the bacterial activities or by the decaying of trash in the sewer. Sometimes, dried P-trap, clogged vents, blocked drain also makes the bathroom sink stink like sewer or rotten eggs.