If your bathroom sink smells like rotten eggs, sewage, or general unpleasantness, it is likely due to a clog or a ventilation problem. The bad smell can be attributed to hydrogen sulfide gas, which is produced as a waste product when bacteria feed on grime and sewage - yikes!

But don’t worry - while the smells can be offensive, they can be remedied. The first step toward getting rid of an unpleasant odor is identifying the culprit. Below are reasons why your sink may stink.

What causes a stinky bathroom sink?

1. Clogged bathroom sink drain: There could be a clog in the drain, whether caused by hair, gunk, soap scum, or something else. If your sink is slow to drain, it’s possible you have a blockage below the basin.
2. Faulty P-Trap: The P-trap is an important part of a sink. This curved pipe holds a small amount of water that creates a barrier between the sink basin and the sewer and prevents sewer gases from escaping through the drain. You should also check underneath the sink for leaks and signs of damage to the P-trap. If it looks broken, this could explain why smelly gases are escaping into your bathroom.

3. Sewer line blockage: Another cause of offensive sink smells is blockage down the drainpipe.
4. Ventilation issues: The ventilation system is also responsible for removing sewer gases from the drains. A blocked air vent could cause bathroom sink smells. To check for a ventilation problem, run water in the sink, flush the nearest toilet, and listen for gurgling sounds coming from the sink. This sound means that water flow from the toilet is sucking air through the drain.
5. Mold or mildew: Drains are a perfect home for mold to grow because they’re dark, warm, and wet. Mold growth can also cause an unpleasant smell in the bathroom sink.
6. Contaminated water: In some cases, it might be the water itself, not the drain, that is causing the sink to smell. To check if your water is contaminated, fill a glass of water from the bathroom sink and fill another glass from a different sink. If both glasses smell, this means your water may be contaminated. If only one glass smells, the problem is likely isolated to buildup in one drain or faucet.

Is the sewer smell in the bathroom sink dangerous?

Exposure to sewer gases in high doses or over time can cause health problems. Possible side effects of inhaling sewer gas include nausea and dizziness, and can lead to hydrogen sulfide poisoning, which can be deadly. You could also be exposed to airborne pathogens that escape as a result of poor ventilation or damaged sewer systems. If there’s extreme buildup of hydrogen sulfide gas, there is also risk of explosion.

Needless to say, treating a smelly sink drain quickly is important to protect your safety.

Now that you know what could be causing your stinky bathroom sink, it’s time to try methods to eliminate those nasty odors!

Whether you suspect your drain is contaminated or clogged, there’s several techniques you can try:

Use home remedies

Sometimes just the thing for a smelly sink drain is a natural de-clogging agent. Boiling water or a baking soda and vinegar solution can combat clogs and flush away bacteria near the surface of a bathroom sink drain.

Hot water

1. Heat a large pot of water or a full kettle.
2. Carefully pour the water into the sink. If your sink is slow to drain, pour the water slowly or in batches.
3. Test the sink to see if the water drains from the basin quickly. Repeat the method again, if necessary.
4. If the sink function improves, chances are you’ve cured the clog or reduced its size. The hot water may also kill bacteria inside the drain and help to combat the unpleasant smell. Be careful, as boiling water can damage PVC pipes.

Tip: Add lemon juice or essential oils to the water to immediately counteract the odor coming from the bathroom sink!

Baking soda and vinegar

1. Mix equal parts of baking soda and vinegar to create a reactive solution (1/2 cup baking soda: 1/2 cup vinegar).
2. Immediately pour the solution into the bathroom sink drain. The fizzy mixture can work to shift clogs and clean the drain.

3. Block the drain with the sink stopper or cloth and wait for about 30 minutes.
4. Pour hot water down the sink to flush the solution away.
5. Check if your clog has been resolved, and repeat this method if necessary.

Use tools

Tougher clogs sometimes require more than household remedies - and that’s where the plunger and auger come in!

Plunging a bathroom sink

1. Remove the stopper from the sink by twisting it up and to the left. If the stopper is fixed, you will have to locate and unscrew the pivot rod under the sink.
2. Fill the sink with water until the base of the plunger is covered.

3. Place the plunger over the drain to create a seal. Push the plunger down and up for 15-20 seconds. Use force, but don’t be too aggressive - bathroom sink drains are delicate and too much pressure could damage the pipes. Remember to cover the overflow outlet to aid with suction.
4. Lift away the plunger and allow the water to drain.
5. Test the drain to see if the clog has gone!

Using an auger

1. Take out the sink stopper.
2. Insert the auger into the opening of the drain until you reach the blockage.

3. Twist the auger to break up the clog, taking care not to jab at it as this could damage the pipes. If the clog cannot be reached this way, try step 4 - otherwise, remove the auger from the drain and skip to step 8.
4. If your clog is deep in the drain, you’ll need to remove the P-trap. Place a bucket underneath the pipe, then unscrew it with a wrench or screwdriver. Carefully remove the pipe, using the bucket to catch any remaining water.

5. Check if a clog is inside the P-trap by using a tool to scrape inside the pipe. Something like an old toothbrush will do the trick. If the clog is deeper in the drainpipe, use the auger again, feeding it into the pipe until you reach the obstruction.
6. Rotate the auger to break up and remove the clog, then pull it out carefully.

7. Securely reattach the P-trap, making it doesn’t leak when the sink is running.
8. Run hot water down the sink to see if the drain is fully functional.

Use Drano^® products

You can also use a drain cleaner to combat stubborn clogs and address smells from your bathroom sink.

We recommend using Drano^® Max Gel Clog Remover on your blocked bathroom sink. When used as directed, the powerful formula is tough on hair, gunk, soap scum, and other clogs, yet 100% safe for bathroom drains!

Here’s how to use Drano^® to fix a clogged, smelly sink:

1. Measure 16 oz of Drano^® Max Gel and pour it into the clogged drain. For ultra-stubborn blockages, use 32 oz.
2. Allow the formula to work for 15 to 30 minutes.
3. Flush the bathroom sink drain with hot water.
4. Repeat the process, if required. With any drain cleaning product, read and follow all safety and usage instructions.

Check the plumbing, ventilation, and heating system

Sometimes bathroom sink odor is caused by a deep clog that requires more advanced techniques to resolve.

First, inspect the water level inside the P-trap. Locate the P-trap under the sink and place a bucket underneath it in case any water spills out. Remove the P-trap carefully using a screwdriver or wrench depending on the type of fixture.

Check the water level inside the pipe - if it’s completely dry, you’ll need to run water down the drain on a regular basis to fill it and block out the sewer smells. This is an easy fix for smelly bathroom sinks that aren’t used regularly.

If you use the sink regularly and there’s water in the P-trap but it doesn’t fill the inverted ‘P’, the problem is likely related to obstructed ventilation. To repair, you need to climb onto the roof to unblock the vent. However, if you’re not confident about climbing or clearing the vent, don’t hesitate to call a plumber! Here’s how to unblock a sewer vent:

1. Locate the vent opening (usually on the roof above the main bathroom).
2. Remove any buildup or debris, such as leaves and twigs that may be blocking the vent.

3. Use a garden hose to dislodge blockages deeper inside the vent. For best results, turn the hose on its most powerful setting and spray it directly into the vent opening. If this doesn’t shift the clog, you can also use an auger.
4. Test the vent by filling it with water for a couple of minutes - if it doesn’t get backed up, you have successfully removed the clog.

If your problem is with the contamination of the water itself and not the drain, the water heater might be to blame. In particular, the hot water heater magnesium anode rod may be reacting to bacteria present in the tank.

To fix this, you can replace the magnesium anode rod with one made from aluminum and disinfect the water with hydrogen peroxide. Once again, if you don’t feel comfortable doing this yourself, calling a plumber is advised.

If none of these methods work and your smelly bathroom sink persists, you will need to get professional help.

Once you have addressed any plumbing issues, you may want to take these simple steps to help prevent clogs and bathroom sink odors from recurring:

• Weekly water: Pour a gallon of boiling water down the drain once a week to keep your sink clog-free. Make sure to regularly let water run down unused sinks to keep the P-trap full and avoid any unpleasant smells.
• Keep it clean: Clean your sink and drain frequently to prevent nasty buildup. Boiling water and lemon works can be used as a natural drain cleaner.
• Proper maintenance: Schedule annual maintenance checks with plumbers to keep your drains running well. Yes - we’re talking to you dedicated DIYers - it’s important to get a professional review now and again.
• Drano: A great way to help prevent a smelly bathroom sink is by using Drano^® Max Build-Up Remover on a monthly basis to stop clogs from forming.

And there you have it - Drano’s tips on how to ease the pain of those smelly sink drains! If you’ve got more clog concerns, explore our Clog Basics blog for advice on beating all types of household blockages.

Discover our full collection of easy-to-use and effective drain unblocking products here.