Why Does My Bathroom Sink Smell When I Run Water? Fix It Today!

You turn on your bathroom sink, and suddenly, a bad smell hits your nose. You wonder what is going on. The truth is, this happens to many people, and the smell usually comes from the drain, not the water. It can be because of dirty pipes, a dry P-trap, or even mold growing inside. In this article, you will learn the exact reason why your bathroom sink smells when water runs and how to fix it completely in simple, easy steps.

Find Out Where the Smell Is Really Coming From

Before you do anything else, the first thing you should do is figure out where the bad smell is coming from. When you turn on the sink and smell something bad, it might feel like it’s the water itself. But most of the time, it’s not the water — it’s the drain.

The smell can come from the sink drain, the overflow hole, the pipes under the sink, or even mold hiding around the edges. Some people panic and think their water is dirty, but that is very rare. If your water smells bad from every faucet in the house, then yes, maybe the water is the problem. But if only your bathroom sink smells when water runs, it’s likely a problem in the drain.

To test it, fill a glass of water from the bathroom sink and smell it far from the sink. If the water smells fine in the glass, the smell is coming from the drain, not the water. This simple test helps you know where to focus your cleaning and fixing.

Another spot to check is the overflow hole. That little opening near the top of the sink bowl often collects soap scum, toothpaste, and even mold. When you run water, air pushes out of that hole, and the smell comes with it. Gross, right?

Now go under the sink. Smell near the pipes and the trap. If the smell is stronger down there, you might have a leak or a dry P-trap, which can let sewer gas come back into your bathroom. Sewer gas smells like rotten eggs and is very unpleasant.

Some people also forget about their toothbrush holder, damp towels, or even the sink cabinet where water has leaked and made mold. So be sure to check everything around the sink too.

• Smell glass of water far from sink to test water
• Check drain and overflow hole for gunk and mold
• Smell under the sink and near pipes for sewer gas
• Look for leaks, mold, or damp items nearby

Clean the Bathroom Sink Drain the Right Way

Now that you know the smell is coming from the drain, it’s time to clean it properly. A lot of people only splash water or pour some cleaner and hope for the best. But that won’t fix a smelly sink. You need to clean deep inside the drain where the smell is hiding.

Start by removing the sink stopper. If it’s stuck, you might need to twist or pull it out gently. Once it’s out, look down the drain. You might see hair, soap scum, or black gunk. That gunk is what smells bad when you run water and stir it up.

Use a drain brush or even an old toothbrush to scrub the inside of the drain. You can also use a wire hanger or drain snake to pull out any hair or buildup stuck inside. Be ready — it’s going to look nasty, but this is what’s causing the smell.

Next, pour a mix of baking soda and vinegar down the drain. First, pour about half a cup of baking soda into the drain. Then, pour a cup of vinegar. It will bubble and fizz — that’s a good sign. Let it sit for at least 15 minutes.

After that, pour a full kettle of hot (not boiling) water down the drain to flush everything out. You can also repeat this process once a week to keep the drain fresh.

Don’t forget to clean the overflow hole. Stick a brush in there and scrub. You can pour baking soda and vinegar in that hole too. Let it fizz and rinse with hot water.

Some people like to use bleach, but only use a tiny amount and rinse well. Too much bleach can damage your pipes or mix with other cleaners and make dangerous fumes.

You can also use enzyme drain cleaners. They eat the organic gunk naturally and are safer than harsh chemicals. They take longer, but they work well if you keep using them weekly.

• Take out the stopper and clean it
• Remove hair and gunk with brush or snake
• Use baking soda and vinegar fizz to kill smell
• Clean overflow hole too
• Use hot water rinse after cleaning
• Try enzyme cleaners for long-term help

Check and Fix a Dry or Smelly P-Trap

One very common reason for sink smells is a dry P-trap. The P-trap is the curved pipe under your sink that holds water. This water stops sewer gas from coming back into your bathroom. But if you don’t use the sink often, the water can dry up.

When the P-trap dries, it leaves a clear path for stinky sewer gas to enter. This gas can smell like rotten eggs or worse. It’s very strong, and it can even make you feel sick.

To fix this, all you need to do is run the water for a minute. That will refill the P-trap with water and block the sewer gas again. If you know you won’t use the sink for a long time, pour a little bit of cooking oil down the drain after running water. The oil floats on top of the water and stops it from evaporating too fast.

Sometimes, the P-trap has water but still smells. That could mean the trap has buildup or is leaking. Leaks under the sink can cause mold and musty smells too.

Take a flashlight and look under the sink. Check if there is any drip or dampness near the trap. If yes, tighten the connections or call a plumber if the pipe is cracked.

If your sink is older or poorly designed, the trap might not hold enough water. In that case, you might need to replace the P-trap with a better one that traps smells more effectively.

Also, check that the vent pipe for your plumbing is working. If it’s blocked, it can cause pressure problems and suck the water out of your P-trap.

• Run water often to keep trap wet
• Add a bit of oil if sink is unused
• Look for leaks or damp under sink
• Replace old or broken P-trap
• Check vent pipe if problem keeps coming back

Remove Mold and Mildew from Around the Sink

Sometimes the smell is not deep in the drain but around the sink. Mold and mildew love warm, damp places, and your bathroom is perfect for them. You may not see mold clearly, but it can grow behind the sink, under the rim, or in the cabinet.

To clean this, make a simple cleaning mix using white vinegar and water. Spray it on every part of the sink — especially in small cracks and corners. Let it sit for 10 minutes, then scrub with a sponge or brush.

You can also use hydrogen peroxide or tea tree oil if you don’t like the smell of vinegar. Both are great at killing mold. Never mix vinegar with bleach — that creates dangerous gas.

Pull out everything from the cabinet under the sink. Wipe down the inside and check for black spots or a musty smell. If you find mold, spray and scrub just like you did above. Let the cabinet dry completely before putting stuff back.

Check around the faucet and behind the sink. Water splashes can stay in hidden spots and grow mold fast. If you have caulk or sealant that looks black or dirty, you may need to remove and replace it.

Also, check things like your soap holder, toothbrush cup, or hand towel. If they are wet all the time, they might smell too.

• Use vinegar or hydrogen peroxide spray to kill mold
• Scrub all cracks, rim, and faucet areas
• Clean under-sink cabinet and let it dry
• Replace moldy caulk if needed
• Wash or replace smelly bathroom items

Fix Plumbing or Sewer Gas Problems

If the smell still won’t go away after cleaning, there may be a deeper plumbing issue. Sewer gas leaking into your bathroom is not only smelly, but it can also be dangerous. It contains methane and bacteria that can harm your health.

One cause could be a broken or missing vent pipe. These vents let sewer gas escape outside your home. If they are blocked or broken, the gas can build up and push back into the sink.

Another cause is a loose pipe under the sink. Even a tiny gap can let gas leak out. A plumber can do a smoke test to find out where the leak is.

Backflow is another problem. If your plumbing doesn’t have a good air trap, dirty water or smells from other pipes can come back up into the sink. This can happen if your sink connects to the same line as a washing machine or bathtub.

In rare cases, your main sewer line might be blocked or cracked. This usually makes more than one drain smell bad, and toilets might bubble or back up.

• Check for vent pipe block or damage
• Look for loose joints or gaps in pipes
• Consider smoke test by plumber
• Fix backflow issues or broken sewer lines

Use These Tips to Keep Your Sink Fresh

Now that your sink smells better, you want to keep it that way. Good habits can stop the smell from coming back again and again.

Always clean the drain once a week. Use baking soda and vinegar, or pour hot water down after brushing your teeth. This helps wash away gunk before it builds up.

If you have long hair, use a hair catcher in the sink. This stops hair from going down and causing clogs.

Wipe the sink dry after using it. Water that stays can cause mildew.

Use a bathroom fan to keep air moving. Less moisture means less mold.

Open the cabinet under the sink once in a while to air it out.

You can even put a deodorizer in the overflow hole, like a few drops of lemon essential oil or a small gel freshener.

If you go on vacation, remember to run all your sinks when you return. This refills the P-trap and keeps sewer gas out.

• Clean drain weekly with safe methods
• Use a hair catcher to stop clogs
• Keep sink and cabinet dry
• Use fan and air out the bathroom
• Add fresh scent drops in overflow
• Run water after vacations to refill trap

Final Thoughts

A smelly bathroom sink can be really annoying, but it’s usually easy to fix once you know where the smell is coming from. Whether it’s dirty drains, a dry trap, or hidden mold, you now have the tools to stop it. Just follow these steps, and your bathroom will smell fresh again. Keep cleaning often and watch for early signs before the smell gets worse. With small habits, your sink can stay clean and smell-free every day.

Frequently Asked Questions (FAQs)

Is it normal for the bathroom sink to smell when running water?

No, it is not normal. If your sink smells when the water runs, it’s likely because of buildup in the drain or a dry P-trap. When water stirs up the trapped air or pushes air out of the drain, it carries the bad smell with it. Cleaning the drain, refilling the P-trap, and removing mold usually solve the problem. If the smell keeps coming back, there may be a deeper plumbing issue that needs professional help.

Can I use bleach to fix a smelly bathroom sink?

Yes, but be careful. Bleach can kill germs and remove some smells, but too much can harm your pipes. Always use a small amount, mix it with water, and never mix it with vinegar or ammonia. Also, bleach doesn’t remove buildup, just the smell. So, it’s better to clean the drain first using baking soda and vinegar, then rinse with hot water. Bleach should only be a last step or used for mold around the sink edges.

Do I need to call a plumber for a smelly sink?

Not always. You can fix most smelly sink problems yourself with a little cleaning and care. But if you try everything and the smell still comes back, or if you see leaks, hear gurgling sounds, or smell sewer gas often, then it’s time to call a plumber. They can check for broken pipes, vent problems, or deep clogs that you can’t reach. Getting help early stops the problem from getting worse.

Is it safe to pour boiling water down the sink?

It’s okay to pour hot water, but not boiling water. Boiling water can damage some types of plastic pipes or loosen pipe seals. It can also splash back and burn you. Use hot tap water or let boiled water cool for a minute before pouring it down. Hot water is great for melting grease and washing away small clogs. It also helps clean after using baking soda and vinegar.

Can mold grow in the bathroom sink?

Yes, mold can grow in many parts of the bathroom, including the sink drain, overflow hole, and around the faucet. It grows in damp, dark places where water sits. You might not see it, but you’ll smell it — musty, wet, or earthy smells. To stop mold, clean your sink often, dry it after use, and use vinegar spray once a week. If caulk or grout has black spots, it may need to be replaced.

Do I have to clean the overflow hole?

Yes, the overflow hole can collect gunk and mold just like the main drain. When water runs, it can push out air through the overflow hole and bring the smell with it. Use a small brush or pipe cleaner to scrub inside the hole. You can also pour baking soda and vinegar inside to fizz out the dirt. Keeping it clean stops bad smells from escaping and keeps your sink fresh.

Is it okay to use air fresheners for sink smells?

You can use air fresheners to cover up smells, but they don’t fix the real problem. If your sink smells bad, you need to clean the drain and check for other issues first. Air fresheners only hide the smell for a short time. However, after cleaning, using a few drops of lemon oil in the overflow hole or a small deodorizer can help keep it smelling nice.

Can my sink smell because of my water?

It’s very rare. If only one sink smells when the water runs, the problem is likely the drain, not the water. But if all your faucets smell, especially the hot water, your water heater might have bacteria. You can test by filling a glass of water and smelling it far from the sink. If the water smells, you might need to flush your water heater or call your water provider. Most times though, the smell is in the sink itself.