Why Does My Sump Pump Smell Like Sewer?

Tom Gaffey
by Tom Gaffey

Sump pumps, while crucial devices in many homes at risk of flooding, often go undetected. This is because sump pumps are most-often hidden within a basin in the lowest point of your home. They are usually located in the basement, making it even less likely that you notice it. But one way that sump pumps can make themselves known is a foul smell. Your sump pump might even give off a sewage smell, which can be incredibly off-putting and should be remedied quickly.

If your sump pump smells like a sewer you should make sure you do not have a sewage leak, as this is a potentially serious problem. Other causes of sewer smell coming from a sump pump include a dry or cracked sump pump, or stagnant liquid in the sump basin. Basement waste built up over time in the sump basin can also contribute to a sewer smell.

A sewage smell in your basement can range from annoying to intolerable and downright hazardous. Regardless of how extreme or strong the sewage smell, there are really only so many different possible causes for this undesirable odor. Some good news is that many of these issues can be fixed using fairly simple DIY methods. Although it should be noted that some of the cleaning and fixing methods might involve less than enjoyable cleaning.

Five Causes Of A Sewer Smell Coming From Sump Pump

There are several reasons your sump pump might smell like sewage. It is, however, fairly simple to check the pump and the basin to discover the likely root cause. Understanding these five common reasons for sewage smell are the first step in ridding your basement of that terrible stench.

Reason One: A Sewage Leak

If your sump pump smells like sewage, there is a good chance that there is sewage in the sump basin, or somewhere else in the home (which eventually leads to the sump basin). The main reason for sewage finding itself in places it does not belong is a sewage leak.

The primary purpose of a sump pump is to pump out groundwater that finds its way into the home. If there is a sewage leak outside the home, in your yard, for example, you might not notice. All the leaking occurs buried underground so you might not notice. This leak, however, can find its way into your home via sewage-smelling water, which will collect in your sump pump.

If you notice a strong unmistakable sewage smell, you should call a plumber. Sewage leaks can cause major damage and will not fix themselves. Addressing and fixing the problem can save you money in the long run. Best of all, fixing the problem will get rid of that awful smell.

Reason Two: Stagnant Liquid In Sump Pump

Sump basins fill with water, and empty once the float or sensor is triggered. At this point, the sump pump dispels all the water from the basin, removing it from the home. If, however, the sensor has not gone off, the water will collect and sit stagnant in the basin.

The water in your sump pit is by no means pure and clean. It has collected various dirt and bacteria on its journey into the basin. This means that if it is given time to sit stagnant, it will fester. The growing of the bacteria and molds can create a foul smell that can sometimes smell like sewage.

If this is the source of your problem, you will notice foul water sitting in your sump pit. The odds are you will need to repair whatever is faulty with your sump pump (the sensor or check valve most likely). You also may need to give the basin a thorough cleaning once it is drained.

Reason Three: Dry Sump Pump

Having no water in the sump pump can also cause the sump pump to smell like sewage. While this may seem strange, you need to think about the science behind what happens when all the water evaporates from a basin.

If you live in an area with a prolonged dry season, your sump pump might completely dry up. This absence of water might prevent stagnant water, but the absence of water can cause the release of gasses. While you don’t want lots of water sitting in your pump, it does require a small amount of water in order to prevent these gaseous smells.

To remedy this problem, clean out the basin (since it’s already empty), and then add a small amount of fresh and clean water to the basin. Allow the pump to run this freshwater through, leaving a small amount still in the basin to prevent the gasses from returning.

Reason Four: Damaged Sump Pump Or Cracked Sump Basin

Another possible reason for a sewage smell is a problem with the pump or basin itself. A damaged or clogged sump pump can give birth to all sorts of issues. In addition to causing the stagnant water issue, pumps can get clogged and dirty with filth that can cause the sewage smell. If a pump is damaged it can cause all sorts of problems that can lead to bad smells. If there is a foul smell coming from your sump pump and you notice it is not working properly, there is a good chance you need to replace your sump pump.

The sump basin can also become damaged. Just like the home’s foundation, the sump basin can also become vulnerable over time. If it is leaking, all sorts of liquids can find a way into the basin. A cracked basin can cause a sewage smell, and can also make your pump work overtime. Make sure you check the basin’s integrity any time the area is cleaned or otherwise maintained.

Reason Five: Basement Waste Buildup

The water in sump basins is not nearly crystal clear or filtered. It is, in fact, often rather dirty. Even with water pumping out, there can be layers of film, grime and dirt that cling to the sides of the basin. The dirt and heavier filth can collect at the bottom of the basin.

At first this might not be a major issue. Over time, however, if left unchecked the filth and grime can build. This combination of dirt and bacteria can combine to create a bad smell. After all it will essentially become its own sewer of sorts if you don’t clean it.

If this is the source of your problem, it might be time to grab the rubber gloves and the scrub brush. The best and often only way to fix this issue is to clean out the basin and remove the source of the sewage odor.

Best Ways To Prevent Sump Pump Smells

Follow A Preventative Maintenance Schedule

In a perfect world, your sump pump will never have a sewage smell for you to fix. While there are several factors that are outside of your control (random sewage pipe leaks), there is a very effective way at preventing sump pump smells and issues. The best way to keep your sump pump running optimally and not smelling at all is to have a preventative maintenance schedule.

A maintenance schedule involves inspecting your pump and the basin on a regular basis. You might need to clean out a filter, or perhaps flush the system. You should also know the proper timeline for replacing your sump pump (often every 7 to 10 years – depending on the sump pump).

Clean Out Your Sump Basin

Another way to get rid of sump pump smells and keep them from becoming overwhelming is to clean out the sump basin. Your sump basin needs cleaning from time to time. The more often you clean your sump pump, the less involved you need to clean it.

You can use a diluted bleach solution to get rid of a lot of the slimy and bacteria ridden water and grit that tends to collect in the sump basin over time. Fresh water is also a good way to flush out the pump as well, and can help prevent the gasses we mentioned in this article.

Hire A Professional To Do The Dirty Work

Sump pumps and sump basins are not exactly the most glamorous parts of the home. Cleaning out a sump basin is likely not on the top of your “DIY dream projects” list either. If you are the type who doesn’t love getting filthy, or if you are sensitive to sewage smells, there is good news.

There are several plumping and cleaning companies that are happy to clean your sump pit. They will also check your sump pump and basin for damage. While this is not something you need to do often, it might be a good idea to call in a professional if you smell something off, or if your sump pump seems to be acting peculiar.

Putting A Lid On Sewage Smells Coming From Sump Pump

If you notice a sewage smell coming from your sump pump you should first make sure you rule out a sewage leak. Sewage leaks can cause the sewer smell in the sump pump and can be a major issue that needs immediate attention. Other possible causes for the sewer smell include stagnant water in the sump basin, a dry or even cracked basin, or dirty water and grime collecting in the sump basin over time.

Tom Gaffey
Tom Gaffey

Tom Gaffey is an expert writer who currently resides in Washington D.C. Tom has a passion for real estate and home improvement writing, as well as travel and lifestyle writing. He lived the last twelve years in Hawaii where he worked closely with luxury resorts and event planners, mastering his knowledge of aesthetics and luxury products. This is where he found his passion for home improvement and a keen interest in DIY projects. Currently, Tom resides in Washington D.C, and also working on his debut fiction novel.

More by Tom Gaffey