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Why Your Basement Smells Like Sewer (And What To Do About It)

We can all agree that sewer gas is one of the most unpleasant smells known to man. This smell can quickly invade your home due to a multitude of reasons. Not only is the smell unpleasant but it often is a warning sign of a much more serious issue. For this reason, it is important to understand why your home, or basement, in particular, smells like sewer.

Why does my basement smell like sewer? The most common reason a basement smells like a sewer is problems with floor drains or drains in basement fixtures such as sinks, toilets, or washing machines. Sewer smell in the basement can also be a result of poor ventilation or, in the worst-case scenario, damage to your sewer line. We’ll start with assessing the issue and then trouble shoot the solution until your basement smells as good as new.

As you can see, the normal reason behind a sewer smell in your basement is something that should be addressed in a timely manner. Failing to remedy the cause of sewer smell could lead to serious damage to your home. In this post, we will share more information on a few of the most common reasons your basement smells like sewer. We will also share some tips for solving this issue and important signs that it’s time to call a professional to handle the unpleasant odor.

Whether you have an unfinished basement that you use for storage or a finished basement that acts as the main living space in your home, sewer smell is an unpleasant inconvenience. Not only is a sewer smell emanating from your basement embarrassing but it could also signal a serious problem that requires professional attention. For this reason, it is important to understand the various reasons behind the putrid odor. 

Reasons Your Basement May Smell Like Sewer

Likely your first response to sewer smell in your basement is to conduct a visual inspection of the area. This is a wise step, however, you are unlikely to discover the cause of the odor in this way. Most times, you will need to do a bit more investigating to uncover the origin of the stinky sewer smell in your basement. Start with the floor drains and ventilation as these are quicker and easier to assess. If it’s not the drains or ventilation, then move to the ejector pump and sewer line. 

Common Problems with Your Basement Floor Drain 

The most common cause of sewer smells in the basement is a problem with your floor drains or drains in basement fixtures. While they are rarely used, your basement likely has several floor drains throughout the floor plan, designed to aid in draining should the basement flood. When these drains aren’t functioning properly it can cause your whole basement to stink.

These floor drains are designed to hold a small amount of water, sealing the pipe so that the sewer gas is not able to invade the home. Although this design works wonderfully the majority of the time, if that seal begins to dry, the sewer smell leaks into the basement. A dry seal is the most likely reason your basement is smelling like sewer. A similar issue can occur with the drains in fixtures throughout your basement. The drain seal in sinks, toilets, or even washing machines will eventually begin to dry if it is not used frequently. Anytime a seal begins to leak, there is a high likelihood that the nasty sewer smell will escape. 

Additionally, if the seal was not installed properly, something that commonly occurs with the seal surrounding the toilet drain, it will begin to leak even if it is not dry. If you are experiencing a sewer smell in your basement, the first thing to do is to carefully inspect every drain in your basement.

Why Your Basement Smells Like Sewer (And What To Do About It)

How to Fix Your Basement Floor Drain

As mentioned previously, the first step is to check all of the floor drains in your basement. You will also need to inspect the drains in basement fixtures such as your toilet, sink, or washing machine. Fortunately, problems with the floor drains are an easy fix!

If you suspect that a dry seal in your floor drain is causing the sewer gas to escape, slowly dump a gallon of clean water down the drain. This will reseal the pipe, preventing the odor from invading your basement. If you are desperate for relief, you can also add a small amount of a mild household cleaner to help mask the scent.

Issues with seals around your toilet, sinks, or washing machines may require a more aggressive approach. However, it is wise to first try running water through the fixture or flushing the toilet to replenish any water that has dried up.

Is my basement floor drain clogged?

Your drain could also be clogged this would cause anything poured down the drain to be trapped. It’s a common plumbing problem for your basement floor drain to become clogged. There is a u shaped trap in the drain the can often get items stuck in it or build up with blockage over time. When it is blocked anything that stacks up in the drain can begin to stink. The smell can be similar to sewer gases depending on what has been put down the drain.

Can you plunge a basement floor drain?

Yes, you can use a plunger to attempt to clear out the basement floor drain. Using a normal plunger to get a simple clog out of your basement drain could save you hundreds of dollars to have plumber come out and do the same job. This may or may not fix the issue but it could be what you need to get things flowing again.

How can I improve my basement ventilation?

If your basement was finished after the house was complete, there is a good chance that your basement bathroom or laundry room ventilation system is poorly done. If the ventilation is not tied in with the remainder of the home ventilation system, the sewer gases originating from the basement may not have a clear escape route. 

It could also be a problem in other areas of your home that is causing the basement odor! Poor ventilation on other floors of the home could be causing sewer gas to leak into the basement. After checking the drain seals in your basement, take some time to confirm that your home is ventilated properly.

To the untrained eye, it may be challenging to confirm that the home is properly ventilated. If you can do so, confirm proper ventilation or contact a professional for assistance. In the meantime, do your best to locate the source of the smell (whether in the basement or upper floors of the home) and use other forms of ventilation to mitigate the odor.

How do I improve my basement ventilation?

Using fans and a dehumidifier will improve basement ventilation by helping to circulate and filter the air. It would also be good to have a ways for fresh air to enter and exit. Using an exhaust fan or a fan or vent to the basement would help insure circulation. This would help create a better air flow and a more comfortable environment. Natural ventilation through a window is an excellent way to improve ventilation but having an open window may not be a good option depending on the weather outside. If you don’t have windows this may be an expensive option but could also add value to your home and improve the look and feel of your basement.pore basement ventilation

Issue With Ejector Pump

Bathrooms or laundry rooms in the basement often need an additional fixture to pump out wastewater. This is accomplished by an ejector pump that pumps up from the basement and into the sewer system. While this system often performs as it should, some issues may arise over time. Cracks, clogs, or issues with the seal of your ejector pump can lead to a sewer smell that invades your basement.

How do I fix my basement ejector pump?

Fixing the ejector pump is typically not a DIY-type job. If you suspect that the ejector pump is causing the sewer smell in your basement, it  may be best to contact a professional. In the meantime, minimize the use of wastewater in your basement to eliminate undue stress on the pump. If you do enjoy a little DIY project you can purchase a new ejector pump and begin to unhook you current one and replace it. 

sewer sum pump

shower head cleaner

Damage to sewer line could be causing the smell

Likely the first thing you suspect when you smell that awful sewer smell in your basement is damage to your sewer line. While this is unlikely, it is certainly the worst-case scenario. If you have ruled out the other possible causes of the sewer smell, it is time to consider damage to the sewer system. This is a very serious problem. Because of this, it is important to contact a professional plumber immediately. Doing so will eliminate the potential for further damage to your home or sewer system.

Repair the Sewer Line

In some cases, the only way to remove the sewer smell from your basement is to repair the sewer line. If you are unable to remedy the odor with any of the other fixes, you will need to contact a plumber to inspect and repair the sewer line leading to your home. While this may be expensive, it is a necessary step in protecting both your home and your family.


under ground sewer line

Why does my basement smell like rotten eggs?

The smell of sewer gas has a distinct rotten egg smell. The smell comes from hydrogen sulfide that is in the sewer. As organic materials break down there is a gas that is released. The smell is hard to handle and the gas can be a danger. If you smell the “rotten egg smell” coming from your basement it’s vitally important to utilize the steps above to remedy your rotten egg stench and fix your basement. The sewer gases that are released also have ammonia, carbon monoxide and esters. These gases allow can be a hazard. If the rotten egg smell is extremely strong make sure to ventilate the area before addressing the cause. These gases can be harmful to your health and also flammable.

Why does may basement smell like poop?

This is most likely due to issues with the basement floor drain. When the seal in the floor drain pipe drys out it releases sewer gas. The smell that is released is similar to poop or rotten eggs. The smell can move up through the basement and into your home. It’s important that the issue is addressed immediately. The gas that is released can be dangerous to your health.

What Happens if You Don’t Fix the Source of Sewer Smell?

So, what happens if you just ignore the sewer smell in your basement? Won’t it eventually go away? Maybe you will just grow accustomed to the odor? There are actually several reasons why it is important to address the source of the odor as soon as it appears.

Sewer Smell is Unpleasant & Embarrassing

First, and most obviously, sewer smell is both unpleasant and embarrassing. Not only does it make your basement useless but it also creates an awkward situation for guests to your home. Trust us, candles will not cover up the putrid odor of sewer emanating from your basement. 

Sewer Gas Could Contain Harmful Bacteria

Sewer gas is a warning sign of a more serious problem, a sewer leak. In many cases, sewer gas contains harmful bacteria that can lead to headaches and other health concerns. 

Sewer Smell is Indicative of a Serious Issue

If you own your home, you understand the severity of a serious problem with your sewer system. This can be expensive to remedy. However, failing to do so could result in a more serious issue or prolonged damage to your home. It is always important to pay attention to these warning signs to prevent unnecessary home damage. Some damage could be so sever that it could require you to file a home insurance claim

Rid Your Basement of Sewer Smell Once & For All

Unfortunately, most basements do not have windows or doors that you can open for ventilation. Because of this, you will need to find other ways to get rid of the smell after fixing the issue. Many products will effectively help you eliminate the sewer smell once and for all. This will allow you to enjoy every area of your home once again. Consider investing in an odor-absorbing solution or an anti-microbial odor eliminator, both of which have excellent customer reviews. 

While a sewer smell in your basement is certainly inconvenient, consider it a warning sign preventing a more serious issue. With a bit of investigation and a few hours or work, you can eliminate the sewer smell in your basement once and for all!

Thanks for reading! Find more home tips from experts here. 

Written By

Hi there! My name is Matt and I write for Expert Home Report. I enjoy writing about everything related to home improvement, home tips and DIY. In my spare time, I'm either spending time with my family, doing a DIY project or learning a new skill.