Why Bathroom Sink Smells Like Sewer? How to Fast Fix it

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Why bathroom sink smells like sewerToday, stinky bathroom sinks can be embarrassing to you and your visitors. Have you ever asked yourself why bathroom sink smells like sewer? If you have ever met this condition in your bathroom or any other bathroom, you must have wondered why bathroom sink smells like sewer gas.

If you have no much time to go through the details, you can check these two quick solutions to the problem. They will help to keep your best bathroom sink clean and at the same time pleasant-smelling. Check them and where to get them hurriedly.


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As we delve into the details, I want to disclose to you that apart from being unpleasant, the rotten egg smell from your bathroom sink can potentially cause you health problems such as a headache. The gas is insanely hazardous to your health, and its presence should not be ignored.

In the sewer gas, there is a particular form of a gas known as methane. This gas is highly flammable. If you allow the sewer gas to dominate the space in your bathroom, this could be an accident in waiting.

There are various reasons why bathroom sink smells like sewer gas. Sometimes, it could be a smell coming from your toilet. This simple guide will explain to you the potential causes of the offensive odor in your bathroom sink. It will show you the remedies that work quickly to restore freshness in your bathroom. 


How the Sewer Gas Smell is Emitted Through Your Bathroom Sink

Underneath your bathroom sink, there is a p-trap. The p-trap is designed in a way that allows it to prevent the emission of sewer smelling gas into your residential area. If the p-trap is not vented correctly, this could be the potential cause of the sewer smelling gas in your bathroom.

Inside the drain, there is some water that is trapped there. Such water acts as the seal that prevents the offensive odor from being emitted to your bathroom.

In some cases, it is possible that the sink does not get used. This could be the condition in the guest room. If this happens to be the case, the water that creates the protective barrier inside the drain will evaporate.

After the water evaporates, this kills off the protective seal, and this explains why bathroom sink smells like sewer gas. With this condition, the evolution of the bad smell will be inevitable.

Inspecting Why Bathroom Sink Smells Like Sewer

Since you are not sure what is precisely responsible for the sewer smell, you have to do some inspection. In most cases, you will start with the p-trap since it is just underneath your sink and it is the most prominent suspect.

1. P-trap

In inspecting the p-trap, you want to check whether there is water which as I have mentioned earlier that acts as the seal to the offensive smell. The role of p-trap is standard even in showers and tubs. Apart from having that vital water, they may catch any earrings and rings to prevent them from moving to the septic tanks and sewers in case they accidentally fall.

In a poorly designed plumbing system, you are likely to face the issue of smelly drains. Moreover, if the vent pipes are clogged, this will cause the water in the p-trap to be absorbed by the clog. Vermin and sewer gas will then find an escape route to your bathroom.

Now, you want to determine whether this is the case in your bathroom. You have to turn the faucet valve on and allow some water to flow down the drain. If the issue were the dry p-trap, this would easily be solved. In such a case, you will be advised to regularly allow some running water down the drain to fight the effect.

2. Inspecting for Possible Biofilm in the Tailpiece

Inside your shower drain, tub and bathroom sink, the likelihood of having a bad smell is high. It is just the same case with kitchen sinks where odors can be a common occurrence. Inside every sink, there is a pipe known as the tailpiece. 

Tailpiece connects the p-trap to the bottom of the sink. In your bathroom, this type of pipe is usually exposed. As the grime, dirt, and bacteria move to the septic tank, it passes through this pipe. 

With time, a layer of slime begins to grow along this pipe. In this condition, bacteria and mold growth are enhanced. Such substances become the reason why bathroom sink smells like sewer. 

In simple terms, the thick layer of slime is now the biofilm. In this conditioning, mold gets boosted to grow faster. You run some water down the drain; spores get ejected into the air. The offensive gas is responsible for such an explosion, and this is why bathroom sink smells like sewer. 

3. Water Heaters

If after inspecting all other areas, you still don’t find the source of the sewer gas in your bathroom, it is time to examine the water heaters. If a water heater has not been used for some time, it can emit this noxious egg-like gas.

There will be organic matter trapped within the system which will trigger the bad smell. If your water heaters have not been used for a while, it is recommendable to flush some water in them. This will help to bring a different breath around your residential setting.

Primary Reasons Why Bathroom Sink Smells Like Sewer in Most Homes

When you sense an unpleasant smell in your bathroom sink, you will likely point out in specific areas. The sink drain is the primary culprit.

1. Bacteria Build-Up in the Bathroom Sink Drain

When bacteria are allowed to grow down the drain, they will eventually lead to the evolution of foul smell. If you smell such as an odor, there is a likelihood of bacteria builds up down the drain and this is also likely going to make your bathroom sink clogged. It is always a sewage-like odor or rotten egg smell. According to research, the bathroom drain is the primary reason why bathroom sink smells like sewer.

Bathroom sink drain has all the organic matter that flows down with the water. There is soap, hair, and used toothpaste spits. It is the accumulation of such used substances that lead to the emission of the offensive smell.

But the question is; how can you inspect the bathroom sink drain for the stink? Some people ask why bathroom sink smells like sewer when water runs. You can open your faucet and let in some water in a clean glass.

Inspect whether the water is the problem far away from the area. Does the bathroom water smell like sewer when in the glass? If this is not the case, there is no problem with the water. The issue is just in your drain. How do you fix smelly drains? Then you will have to flush the drain.

2. Clogged Venting Pipes are Why Bathroom Sink Smells Like Sewer

After finding out whether the water was the cause of the sewer-like smell, probably, you have realized this was not the cause. You thought it was the sink drain but after working on it, the problem is not resolved, and still, bathroom sink smells like rotten eggs.

Trust me; there is a likelihood that there is an issue with your venting pipe. When the venting pipes are correctly installed, they won’t allow the sewer gas to get into your bathroom. These pipes are supposed to take the back-flowing offensive gases into the roof. At the point, the gasses are safely emitted and do not present any potential hazard.

In some cases, these venting pipes get clogged, and this complicates the path through which the sewer gas should be passing through. In such an event, these gases will try to find routes elsewhere. They will try to find a way out through your bathroom drain. Then this explains why bathroom sink smells like sewer. 

What Should I do With a Clogged Venting Pipe?

If the issue is the clogged venting pipe, you will have to invite the services of a professional plumber. These pipes become filled with debris, and it has to be removed to restore normalcy. Alternatively, it is likely that the person who initially installed them failed to meet the highest installation standards.

In some cases, the person doing the initial installation can vent these pipes in the wrong direction. If this happens to be the case, this presents the trouble of a smelly bathroom area. In fact, you can feel the smell from the walls, and the poorly vented pipes majorly cause this.

Also, it is possible for the vent pipe to develop a crack. A crack will allow the sewer gas to escape and ruin your stay at home. If you call a professional plumber, they are likely to use a smoke machine to find the exact location of the crack. 

3. Blockage in the Sink’s Overflow

Finally, the blockage in the sink overflow could be the reason why bathroom sink smells like sewer gas. First, inspect whether your bathroom sink is designed to have an overflow mechanism. If the sink gets overfilled, the overflow mechanism offers some relief.

The overflow hole can build grime with time. The filth becomes the source of the sewer-like smell in your bathroom. How can you fix this? You can use a bottle brush to wipe out the buildup. 

How to Get Rid of the Sewer Gas in Your Bathroom Sink

In most cases, if you smell sewer-like gas in your bathroom sink, there is an odor escaping through your drainage system. Before you contemplate about calling a plumber, you can always try to use cost-effective measures. As discussed above, the issue could be brought about by a dry p-trap or a clog.

You will have to understand that if the plumbing system was done correctly, this should not be a concern to you. You can employ the DIY actions that are recommended for this circumstance by the experts.

Follow the step-by-step DIY tip to check whether the issue will be resolved. If there is no major issue, the stinky drain should be fixed.

1. DIY Tips to Fight the Offensive Sewer Gas in Your Bathroom Sink

  • Measure a half cup of baking soda and pour it in the bathroom sink drain.
  • Measure a cup of vinegar and add to the baking soda inside the sink drain.
  • Let the bathroom door remain closed for one hour to allow the reaction to take place with no interference.
  • In the meantime, prepare some hot water and pour it down the drain once the one-hour timeline elapses.
  • Important! Pour some cold water down the drain fifteen minutes after pouring the hot water. This should rinse off the vinegar.
  • Measure a cup of chlorine bleach, pour it down the drain and allow it one hour. Close the bathroom door again and leave it.
  • In the meantime, prepare some hot water which you will pour down the drain after the one-hour time limit elapses.
  • Now, allow cold water to run from the faucet for fifteen minutes. The p-trap will trap some amount which is recommendable.
  • At this point, the problem should be resolved if the dry p-trap or clogged drain caused it. 

2. Use Bottle Brush and Oxygen Bleach

The bottle brush and oxygen bleach are worth to try out if you are having the issue of a stinky bathroom sink. Sometimes, you perform the cleaning of the bathroom sink, but this is never effective at times.

You will notice that there are fixed metal parts at the bottom of the sink which is hard to clean. You have to dismantle the system to enable adequate cleaning. In doing this, you can clean the inside of the pipes. Remove the gaskets and rubber washers under the sink to adequately clean the system.

In the event of an old sink, you can replace the gaskets and rubber washers. This will help you to counter any possible leakages. When you are done with cleaning, re-assemble all the parts correctly.

How do I Use the Oxygen Bleach and Bottle Brush?

I recommend the use of stain solver certified organic oxygen bleach in this case. You will have to dissolve two spoons of the stain solver certified organic oxygen bleach in a quart of hot water.

After that, pour the mixture in the drain, and use the bottle brush to scrub the piping system. Clean the p-trap and the tailpiece pipe. In doing this, remove the sink stopper to enable the insertion of the bottle brush down the drain. Use an adjustable plier to remove the stopper. 

3. Resolving the Biofilm Issue

In your vanity sink, a biofilm is likely to grow on the inner parts of the overflow hole. In this case, you can use a turkey baster and stain solver solution to remove the biofilm. Squirt some amount of this solution in the overflow mechanism and allow fifteen minutes of reaction. 

Come back and do more squirts down the overflow mechanism to remove all the biofilm. Try to perform the squirts at a fast speed as this way is most effective. Within an hour, the problem should be resolved. 

4. Invite the Services of a Professional Plumber

The final option that you have if the bathroom sink still smells like sewer gas is to call a plumber. A plumber is a professional who is specialized in resolving such issues. It might be a problem that is beyond your understanding, and this implies that it is reasonable to invite a professional plumber. 

I recommend that you call a plumber who is insured, bonded and licensed. Just ask for a recommendation for such a plumber in your area, and you will get assisted. You can also do an internet search for a local plumber in your area who meets these specifications. 

The reason I give this advice is that you have to avoid getting cheaper services which will not resolve your issues. Call a plumber who will be accountable and can improve the efficiency of your system.


In summary, you can encounter the bathroom sink issues such as the rotten egg smell. Sometimes, your entire house might smell like sewage. In such moments, you ask yourself, what is the smelly bathroom sink drain remedy? You confuse that it is likely that the kitchen sink smells like sewage.

Other family members are all saying bathroom smells like sewer when water runs. Then your question is; how do I get rid of smelly drains? How do I fix smelly drains? If your bathroom sink smells, this post must have been helpful to you. People struggle to establish the source of the problem, but this post offers a comprehensive breakdown.

Why Bathroom Sink Smells Like Sewer? How to Fast Fix it was last modified: by