Reasons Why Your Bathroom Sink Smells + Ways to Fix it!

The following scene is probably all too familiar with many homeowners out there: you’re brushing your teeth and you bend down to spit the toothpaste out only to be greeted by a foul stench coming from your drain. It happens to the best of us but you don’t have to put up with it.

In this article, you will learn what causes these unpleasant odors in your sink and some simple fixes.



One of the most likely culprits of sink odors is from biofilm, a collection of microorganisms that build upon a surface over time. Biofilm can consolidate on virtually any surface and is known to emit an unpleasant odor.

Biofilm buildup is so common in bathroom sinks because your sink pipes see a lot of waste material every day. Think about how much toothpaste, mouthwash, hair, skin products, shaving cream, and dead skin cells pass through your sink daily. All of these kinds of materials breed biofilm.

You likely don’t have a powerful air conditioner blasting into your bathroom at all hours of the day which is another reason stinky biofilm loves bathroom sinks: microorganisms and bacteria that make up biofilm love room temperature to warm climates.

The warm water running in your bathroom sink faucet provides the perfect temperature for biofilm to form.

Biofilm is generally black and slimy. You probably have it in your bathroom drain pipes right now even if you don’t smell anything. It takes time for biofilm to emanate a scent but it is almost always present.


If you are detecting a hint of rotten eggs in your bathroom then the culprit is most likely hydrogen sulfide. Sulfur can be created in the ground, in your pipes or in the water that passes through them. In the bathroom, it is usually formed through the natural activity of bacteria.

It’s important to remember that not all bacteria are bad. In fact, in the case of your pipes, bacteria usually helps to break down the residue that passes through them so they don’t get clogged. The problem is that when bacteria break down materials and clear it away, gas is left behind.

This gas ladies and gentlemen is what we call hydrogen sulfide or sewer gas.

Sulfur will usually smell like eggs well past their prime. It can be coming from more than one source which makes it a particularly troublesome problem to handle.


All homes with plumbing are linked to the sewers so that all water waste can be disposed of sanitarily. The problem is that sometimes sewer gasses and smells can run up through these pipes and leak into your home.

This is typically caused because of a malfunctioning P trap. A P trap is a bit of a misnomer because the pipe is actually shaped like a U and it is directly under your sink. The purpose of this pipe is to block sewer gasses from creeping into your bathroom with water.

A properly functioning P trap will always have a reservoir of water to block gas.

When bathrooms are used infrequently though, the water reservoir could dry up resulting in sewer gasses seeping into your bathroom.

Another way that sewage smell travels into your home is through the plumbing vents. Plumbing vents are installed in all plumbing systems to let such gasses seep out and to channel them outdoors so they don’t stink up your house. These vents are prone to blockage though which means gas can revert into your home resulting in that funky, sewage smell.


bathroom sink smells

Quick Fixes for Your Smelly Sink

So does your bathroom smell weird? Before you call a Dallas plumber there are some simple fixes that you can try right now.

  • The first step is diagnosing the smell. Try taking out the sink stopper. If it is covered in a black slimy residue, you have biofilm on your hands.
  • Luckily biofilm is not hard to get rid of. You can simply pour half a cup of bleach into your sink drains or if you prefer a half cup of baking soda with a chaser of a cup of vinegar will do the trick.
  • Another mixture of ¼ cup of salt and half a cup of baking soda followed by a cup of vinegar could also be used for stubborn biofilm. This mixture sparks a foaming action in your pipes and the salt helps to scour them.
  • It is extremely important to note at this point though that you should NEVER mix bleach and ammonia or bleach and Drano. These combinations form chloramine or mustard gas that is poisonous and could be deadly.
  • Running hot water in bathrooms that aren’t used frequently will fill the reservoir in the P trap and could instantly eliminate sulfur odors.
  • Your water supply could also be the source of foul odors. Try filling a glass with hot water from the bathroom sink. Take it outside and see if it smells bad. If it does you can try replacing the anode rod in your water heater which may be the source of contamination.

When to Call a Plumber to Help With your Smelly Sink

Unfortunately, not all smells can be taken care of with a quick fix.

If you suspect that the drains need a deep clean or are unsure where the smell is emanating from then you may want to call a plumber.

If you have tried all of the above methods to get rid of the smell to no avail it may also be time to seek professional HVAC help. If you suspect that your plumbing vents may be blocked you will need to call a plumber to clear it and repair it if it has become compromised.

In general, don’t do anything you aren’t comfortable with. Disassembling pipes can cause a lot of water damage and isn’t worth the risk. When in doubt, call a plumber out.



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