Smelly Bathroom Sink Drain? Here’s How To Fix It.

Last Updated On June 22, 2024

Updated on December 7, 2022



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Smelly Bathroom Sink Drain Here's How To Fix It.

If your bathroom sink drain smells bad, it can be a real nuisance. Not only is a smelly bathroom sink unpleasant, but it can also be a sign of a bigger problem.

In this blog post, we will discuss some of the causes of smelly bathroom sink drains and how to fix them. We will also provide some tips on how to prevent this problem from happening in the future. Let’s get started!

In this PlumbingNav article, you will learn: 

What's In This Guide?

      What You Need to Know About Smelly Bathroom Sink Drains

      When your bathroom sink starts to get smelly, it can be an unpleasant experience. This is often the result of “gunk” buildup, which occurs when moisture, hair, organic debris, and soap scum collect in your sink’s drain over time. There are some other causes as well.

      There are a few key things you should know about smelly bathroom sink drains, including what causes them so you can effectively fix the problem.

      What Causes A Smelly Bathroom Sink Drain?

      The most common reason why most homeowners experience a smelly bathroom sink is due to these 3 issues. Let’s discuss each of them in detail. We’ll then outline how you can fix them.

      1. Organic Material & Odor-Causing Bacteria

      There are a few “usual suspects” when it comes to bad odors and sink drains. Here they are.

      Organic Material and Bathroom Sink Smells

      First, stinky drain buildup is typically caused by a buildup of organic matter in your sink’s pipes. For example, hair and soap residue can combine with moisture over time to create a smelly, sticky substance known as biofilm that clings to the sides of drains. This is one reason for the foul smell.

      One type of bacteria is pink. If your bathroom sink has pink stains, you clearly have bacteria present.

      Odor Causing Bacteria and the Bathroom Stinky Bathroom Sink

      Another common cause of smelly bathroom sink drains is the presence of odor-causing bacteria. These bacteria are often present in small numbers in our homes and are not generally harmful.

      However, they can multiply quickly and become a problem if they have the right conditions to thrive. Your bathroom sink provides just that environment.

      A Smelly Recipe for Bathroom Sink Odors

      Some of the conditions that favor the growth of these bacteria include standing water, warm temperatures, and organic matter. When these bacteria multiply, they can release smelly compounds that make your bathroom sink stink.

      2. Clogged Bathroom Drain

      Another common cause of smelly bathroom sink drains is a clog in the pipe. When your drain is clogged, water can build up and stagnate, providing the perfect environment for smelly bacteria to grow.

      You might first notice your sink is slow to drain after brushing your teeth or washing your hands. This is a sign of a clog further down the drain. As water sits, it promotes the smells we discussed above.

      3. Sewer Gas Entering the P Trap

      Sewer gas is produced by the decomposition of organic matter in your home’s sewer system. It is composed of methane, carbon dioxide, and other gases.

      Sewer gas rises through vents while waste leaves your drain and then sewer lateral. However, the smelly gas can enter back through your bathroom drain by the sink trap. A sink trap is a U-shaped pipe that is located under a sink, also called a P-trap.

      So how is the P Trap related to a smelly bathroom sink?

      The sink trap contains water that creates a seal that prevents sewer gas from re-entering the room. When the water in the sink trap evaporates, it allows the sewer smell to pass back through the drain pipe and into your bathroom.

      This can cause a smelly bathroom sink drain that persists regardless of cleaning.

      If you just cleaned your sink and there are no clogs, yet it still smells like sewer gas…ding, ding, ding, this is likely your problem.

      How to Fix a Smelly Bathroom Drain (3 Methods)

      We are going to discuss how you can fix your smelly bathroom sink drain according to the causes we already laid out above. 

      Before giving you detailed steps, here is a video showing you the overall process and where stinky smells might be hiding. 

      Note: We don’t recommend pouring bleach into your sinks or drains. See this link for a similar drain brush as featured in the video, and also an enzyme-eating cleaning agent.

      Now, here are some detailed steps for you to reference.

      How to Fix A Smelly Bathroom Sink Due to Bacteria

      1. Pour a pot of boiling water down the drain to help loosen up any debris.

      2. Add 1/2 cup of baking soda and 1 cup of vinegar to the drain and let it sit for 30 minutes.

      3. Flush the drain with hot water after 30 minutes.

      The white vinegar alone should clear up the basic drain odor. If this doesn’t work, we recommend using a natural enzyme product. This takes it a step further, as the enzymes will “eat” away at hair clogs and other organic material that might be causing the smells further down in the sink trap.

      Pro tip: also pour some in the overflow hole of the sink.

      See this post where we review the best enzyme drain cleaners.

      This method is great to clear up smelly sinks. It’s a great DIY alternative to buying sani-clean drain sticks.

      How to Fix A Smelly Bathroom Sink Due to Clogs

      Now we’ll discuss how to fix your bathroom “sink stink” due to a clog.

      The most important thing you can do is to clear the clogged drain as soon as possible. The longer water sits in your sink, the greater the chance for smelly bacteria to further grow.

      There are four ways you can clear a smelly bathroom sink clog:

      1. Use a plunger: This is often the first tool people reach for when they have a clog in their bathroom sink. See this post for a more in-depth article on how to unclog your bathroom sink if you need more info.
      1. Use a clog removal tool: This is a long, thin, flexible tool that can help you grab and remove hair clogs from your bathroom sink drain. These are available at most hardware stores, and we review the best hair clog remover tools here. If you know a clog is behind the problem, and you need more muscle, you can also use a plumbing snake.
      1. Remove the sink trap and clean it: The sink trap is the U-shaped pipe located under your bathroom sink. This is where many clogs form. To remove the sink trap, you will need a wrench. Place a bucket under the sink trap to catch any water that may spill out. Then, use the wrench to loosen the slip nuts on either side of the trap. Once the nuts are loose, remove the drain trap and clean it with a paper towel or brush. You can also use a wire hanger to remove any debris from the drainpipe.
      1. Use a liquid drain cleaning product: We recommend using a natural, enzyme-based drain cleaner like Earthworm or Green Gobbler for cleaning smelly drains. These are our top picks because they are safe for your pipes. They will eat away at the hair and other organic matter that is causing the clog, and the smelly odors. Tip: You can also pour some in the overflow drain to clear up any bacteria hiding there.

      How to Fix A Smelly Bathroom Sink Due to Sewer Gasses

      As we discussed above, smelly bathroom sink drains can be caused by sewer gasses entering your bathroom through the P-trap.

      How the P Trap can affect bathroom sink smells

      The most important thing you can do to prevent this is to keep the water in your sink trap full. This will create a seal that will prevent sewer gas from escaping.

      You can fix a dry p trap by running water for a few minutes.

      If the water level in the trap does not rise, then you will need to add more water. One way to do this is to pour a pitcher of water into the drain, or just run the cold water tap longer.

      Is this a spare bathroom drain that smells?

      Why didn’t you say so! Bathrooms that aren’t used very often can experience evaporation, but we have a little hack for you. You can also add a small amount of mineral oil, which will help to slow evaporation. By keeping your p-trap full, you can help to prevent sewer gases from entering your home.

      What about proper bathroom sink venting?

      Here is how a bathroom sink is supposed to be vented.

      As mentioned, the bathroom sink has a p-trap, which is a U-shaped pipe that holds water in order to seal off the smelly sewer gases. We discussed how to ensure this is filled with water to restrict sewer gases. However, let’s take this further…

      The p-trap connects to a drainpipe, and the drainpipe goes up into the wall. There should be a vent stack in the wall, and this is what allows air to circulate so that the water can flow down the drainpipe and into the sewer. 

      If there is no vent stack, or if it’s not working properly, then the air will be restricted and the water won’t be able to flow properly. This can cause all sorts of problems, including a smelly bathroom sink drain.

      What can be done? The easiest thing to check is if proper ventilation is occurring due to no air restrictions. You can look in the attic to ensure the vent pipe isn’t disconnected or damaged.

      And, if you’re brave and very careful, you could inspect the vent at the roof to ensure no bird nests, leaves, pine needles, or other debris are restricting airflow. If it’s restricted, just clear it. If you find the vent was not installed properly you’ll likely need to call a plumber.

      Supplies You’ll Need to Fix a Smelly Bathroom Sink Drain

      To begin wrapping this up, we created this handy list of supplies you can use to solve your sink drain smell. We collected this list from our article and the combined causes we discussed. You can find our best choice for each of the products or tools that were mentioned below, in one place:

      FAQ’s on Smelly Bathroom Sink Drains

      Why does my bathroom sink drain smell like sewer?

      The smelly bathroom sink drain is most likely caused by a clog in the P-trap. The P-trap is the U-shaped pipe under the sink that holds water to prevent sewer gases from coming up through the drain. Alternatively, if there is no water in the P-trap, then sewer gas can come up through the drain and cause a smelly bathroom sink. We assume here you confirmed the odor was coming from only one drain versus the entire house.

      How do you get rid of smelly drains?

      To fix a smelly bathroom sink drain, you will need to clear any clogs that might exist in the drain or in the P-trap.

      Start with boiling water and vinegar, and don’t use bleach. You can also use a plunger or plumbing snake to clear the clogged drain or disassemble the P-trap to remove debris manually.

      Alternatively, you can use a liquid drain cleaner to dissolve organic materials, debris such as soap buildup or toothpaste, or other unpleasant odor-causing bacteria.

      Final Thoughts on Smelly Bathroom Sink Drains

      So, what’s the culprit of your smelly sink drain? Chances are it’s one (or more) of these four causes. Luckily, there are solutions to each of these problems! By the way, these methods also apply to a bad smell in a shower drain, kitchen sink, or garbage disposal.

      Have you tried any of these solutions yet? If not, start with the easiest and lowest cost option first. If it doesn’t work and you still notice a sink smell, move on down the list. 

      You can always call a plumbing company, but these DIY plumbing tips will most often resolve it without the need to pay for professional plumbing services.

      Additional Help for Your Water’s Unpleasant Smell:

      Dealing with smelly hot water from your water heater? That requires a different solution! The first remedy to a foul odor from the water heater is a hydrogen peroxide flush. The best long-term fix is a powered anode rod for hard water.

      Related Content:

      See this post about pouring salt down your drain at night.

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      About Plumbing Navigator

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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