What To Do When Your Bathroom Sink Drain Smells Like Sewer Or Mildew

If you’ve ever noticed that your bathroom sink drain stinks, you’re not alone. Sewage, musty or sulfur-like odors are unfortunately a common occurrence, but what causes them? More importantly, how can you rid yourself of those disgusting fumes? I will answer those questions today, so let’s get started to learn how to fix such issues!

Why does my bathroom sink smell

People complaining about bathroom sink smells generally describe such odors as musty, sewage, and sulfur-like. To treat stinky drains in the long run, let’s understand first why such smells occur.

Clogged drain

The most common reasons of stinky drains are dirt or other residue build-up that allows bacteria and mold to grow and make your bathroom smell like mildew.

freshly cleaned bathroom sink

Drains can get blocked due to various reasons including:

  • Hair: when it goes down the drain and mixes with soap and grease, it creates a tangled clog and bacteria quickly start to feed on the debris’ particles
  • Soap: most bar soap contains fat or grease so doesn’t dissolve fully resulting in residue build-up in the drain and pipes
  • Minerals: minerals contained in your water supply can build up in your drain over time causing a nasty blockage
  • Dirt: when you wash extreme dirt down the drain it mixes with the other inhabitants and the resulting mud is sure to smell
  • Foreign objects: rings, toothpaste caps, pebbles, and other small culprits lead to blockage in the pipes that can easily lead to stinky clogs
  • Food: washing food down the drain (intentionally or accidentally) is a recipe for clogs, smells, and even bugs

Plumbing system errors

Another common problem is when the bathroom sink smells like sewage that usually happens because of problems in the drain system: a blocked plumbing vent, empty P-unit, cracked pipes or broken components caused leaks can be responsible for a sewer-like smell coming from the sink.

water flowing freely in bathroom sink drain

If a clogged drain vent or dried-out P-trap leads to stagnant odors, most probably a good flush will solve the problem, however, if you suspect a plumbing error, it is better to call a professional.

Water contamination

Another common complaint is that the bathroom sink smells like rotten eggs. Experiencing sulfur odors might make you worried, but this happens probably due to the above-mentioned reasons including bacteria build-up in the pipes that lead to hydrogen sulfide gas forming, a blocked plumbing vent, or dry P-unit allowing sewer gases to rise out.

bathroom sink with water flowing

However, there is another factor you need to check out if there is a strong rotten egg smell in your bathroom, which is your water source. Hydrogen sulfide naturally occurs in well water which can make it stink like sulfur, but up to a certain concentration, it poses no known human health risk.

Also, your water heater or water softener can be responsible for sulfur-smelling water; they have a magnesium anode rod that produces smells when reacting with bacteria in the water. In this case, changing the magnesium anode rod to titanium will solve the problem.

How to clean a smelly bathroom sink drain – Best methods explained

Now that we’ve learned what can make bathroom sink drains to smell, let’s find a powerful smelly bathroom sink drain remedy!

The first step when it comes to cleaning a stinky sink drain is investigating if there is a clog somewhere since no matter what deodorizer you put into it if it can’t pass through the whole system, it won’t reach the source of odors. So, peek into the drain as well as the pipes. Sometimes, the clog will be near the top of the drain, and you’ll be able to see it and fish it out.

Sink Snake Cleaner

FlexiSnake Drain Weasel Sink Snake Cleaner

  • instant clog remover with 360-degree rotation and extra-long, 18 inches design
  • patented micro-hooks locks into hair, filth and grime without damaging your pipes or catching on drain parts
  • ultra-thin and flexible, winds around curves and slips into most drains and grates without disassembling the drain stopper

If you can’t see the clog, use a drain snake which is a think, flexible rotation tool covered in tough bristles to remove hair and grime from the inside of the pipes. When the system is free of debris, you can finally start to deodorize the stinky drain!

Disinfect with bleach

Bleach is probably one of the most well-known drain odor eliminators. It makes sense, given that it is a powerful disinfectant that kills bacteria and bacteria is what causes the unpleasant smells.

To resolve a stinky bathroom sink, here’s how to use bleach:

  • Pour half a cup of bleach down the drain
  • Let it sit for about 15 minutes
  • Flush the drain with about a gallon of water
bottle of bleach

Cleaning smelly drains with bleach can be done when there is already an odor, but also as a preventative measure. But keep in mind that bleach will help only stop the drain from stinking and is not meant to dissolve and remove blockages in the pipes, so before using it always check if the system is not clogged.

Stop odors using vinegar

Another way to stop unpleasant odors that are emanating from your drain is using vinegar. Due to its acidic properties, vinegar helps keep your bathroom smelling fresh in a chemical-free ways and removes smaller clogs. If you have, use concentrated cleaning vinegar which is more powerful than normal vinegar.

30% Pure Vinegar

HARRIS 30% Pure Vinegar Extra Strength

  • 30% industrial strength, 6x more powerful than standard vinegar
  • replace many harmful and expensive commercial cleaning products, excellent to clean patios and driveways, eliminate odors from laundry, and much more
  • can be used diluted with up to 60 parts of water

To eliminate sink drain smells with vinegar, follow these steps:

  • Run hot water to warm up your pipes so residue gets loosened up
  • Pour 2-4 cups of vinegar into the drain
  • Let it sit for about ten minutes. Don’t be alarmed if you hear fizzing
  • Flush the system with hot water to remove the solution

This method is even more powerful if you heat up the vinegar (but do not boil it).

Deodorize with baking soda

To boost the power of vinegar, add sodium bicarbonate (baking soda) to your cleaning solution! These two ingredients are highly effective when it comes to cleaning and can be used in several ways. Their foaming action works wonders when your bathroom drain stinks.

sodium bicarbonate baking soda powder

Here is how to make a baking soda cleaning solution:

  • The first step is to heat a few cups of water to boiling point
  • When the water is ready, squirt some dish soap into the drain. This will help loosen residue
  • Pour the boiling water down the drain. It will mix with the soap and remove dirt and grease from your drain
  • Measure out one cup of baking soda and pour into the drain
  • Then, pour one cup of white vinegar down the drain.
  • The chemical reaction that occurs will result in fizzing which will break up clogs
  • When the fizzing has stopped wait five minutes and then pour two cups of boiling water down the drain to rinse it

Author’s Tip: For more tips, read my How to clean the bathroom with vinegar and baking soda post too!

Use drain sticks

If you still notice a smell after trying these methods, there are still a few tricks to consider before calling your plumber; my favorites are enzyme drain sticks. Such products contain highly concentrated, slow-dissolving enzymes that eliminate foul odors and help break down build-up from grease, soap scum, or hair.

Drain Strips

Green Gobbler BIO-FLOW Drain Strips

  • slow-dissolving enzyme sticks to eliminate foul smells and prevent future clogs and backups in household drains
  • easily breaks down grease, fats, oils, soap scum, food and organic build-up
  • won’t harm drains, pipes or septic systems

Just simply insert the stick into the drain and let it do the magic. My personal experience is that it initially takes a couple of days for the sticks to start working, but if you use them regularly, your drains will be smelling fresh and flowing freely!

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