You walk down to the basement and there it is again, that unmistakable, sharp, rotten smell of sewer. You check the drains, you sniff and sleuth around the laundry sink, but you still can’t seem to pin it down. If you’ve ever asked yourself, ‘Why does my house smell like a sewer?’ you’re far from the only one.
Tracking down pesky sewer smells is work our plumbers do in Chicago basements, bathrooms, and crawl spaces dozens of times every week. For 33 years, Baethke Plumbing has faced these funky smells head-on, earning an A+ BBB rating and the 2011 BBB Torch Award for Ethics along the way. From a floor drain that simply dried out to a forgotten pipe sealed behind a wall during a renovation, we’ll sniff out your problem.
We’ll explore the most likely cause of the smell in your home, whether sewer gas is something to worry about, and why the odor seems to show up only at certain times. Many of these problems have a surprisingly easy fix, and we’ll show you how to tell when it’s something you can handle yourself and when it’s time to bring in a pro.
In most Chicago homes, a sewer smell comes from a dry drain trap in a floor drain, laundry sink, or rarely used shower, and running water down the drain usually fixes it. If the smell keeps coming back, the cause may be a bad toilet seal, an unsealed ejector pit lid, corroded vent pipes, or an open pipe behind a wall, which needs a licensed plumber.
Where Is the Sewer Smell Coming From?
When our licensed plumbers are in your home trying to locate a sewer smell, our first question is always the same: where do you smell it most? In Chicago homes, the answer is usually the basement.
Your basement often has plumbing fixtures that rarely get used, such as:
- Floor drains
- Laundry sinks
- Basement showers or bathtubs
- Basement toilets
Narrowing down the area where the smell is strongest helps us find the source and fix the problem much faster.
What Is the Most Common Cause of Sewer Smell in a House?
The number one reason a house smells like sewer is a dry drain trap.
Every drain in your home has a trap, a curved section of pipe that holds a small amount of water. That water acts as a seal, blocking sewer gases from rising out of the drain and into your home.
When a fixture isn’t used often, the water in the trap slowly evaporates. Once the water level drops below the bend in the trap, the seal is broken and sewer gases can escape. This is especially common with basement floor drains, laundry sinks, and showers or tubs that almost never get used.
The fix is often simple: run water down the drain. Pouring water into a floor drain or running the faucet in an unused sink or shower refills the trap and restores the seal. Running water through rarely used fixtures on a regular basis also flushes out stagnant water and keeps the traps from drying out again. For floor drains you rarely use, pour in water once a week.
If the smell comes back quickly even after you refill the trap with water, there may be a crack in the pipe or another hidden problem. At this point, it’s time to have a professional plumber make a house call to explore the problem further.
Other Common Causes of Sewer Smell in Your House
If refilling your drain traps doesn’t solve the problem, one of these issues may be to blame.
- A failing wax seal usually makes the smell strongest right around the base of one toilet, and it often gets worse right after you flush. Give the toilet a gentle push. If it rocks or wobbles, the seal has likely shifted.
Other signs include water pooling around the base, a soft or discolored floor next to the toilet, or a water stain on the ceiling below an upstairs bathroom.
- If the smell is strongest in the basement near your ejector pit, start with the lid. The odor often gets stronger when the pump runs, like after laundry or using a basement bathroom. Look for gaps around the lid’s edge, missing or loose bolts, a cracked or missing gasket, and unsealed openings where pipes and cords pass through. A properly sealed lid should sit flat and tight, with no gaps you can see daylight or feel air through.
- Corroded vents are the hardest cause to find, because the pipes are hidden inside walls and ceilings. The smell usually isn’t tied to one fixture. It may seem to come from a wall or ceiling, and it can come and go with the weather or when drains are running. Rust-colored stains, water spots, or damp patches on walls and ceilings are warning signs, especially in older homes with galvanized vent pipes. To pinpoint the leak, a plumber can run a smoke test, which pushes harmless smoke through the vent system so it shows exactly where it escapes.
- On one call, Josh, a licensed Baethke plumber, had to open up a wall to find the source of a sewer smell. Years earlier, during a renovation, someone had cut off an old drain pipe, left it wide open, and drywalled right around it, so it was still connected to the sewer line and venting sewer gas straight into the wall. Capping that pipe properly is what finally stops a odor like this, and it’s why finding exactly where the smell is the strongest matters so much.
If any of these causes sound familiar, it’s time to call a licensed plumber. Each one needs a professional repair to make sure the smell goes away for good.
Is Sewer Gas in Your House Dangerous?
A faint sewer smell is usually more unpleasant than dangerous, it’s not the kind of situation where you need to evacuate your home. Sewer gas can contain hydrogen sulfide, methane, and ammonia, and how much of a concern it is depends on how strong the smell is and how long it lasts. According to OSHA, repeated or prolonged exposures may cause eye inflammation, headache, fatigue, irritability, insomnia, digestive disturbances and weight loss. If the odor is strong or doesn’t go away and you experience any of these symptoms, have it checked promptly rather than living with it.
One important safety note: natural gas also has a rotten egg odor. If you smell rotten eggs near your furnace, water heater, stove, or gas meter, don’t assume it’s sewer gas. Leave your home right away and call Peoples Gas or 911 from outside.
Why Does My House Smell Like Sewer Only Sometimes?
If the smell comes and goes, pay attention to when you notice it. The timing is often the best clue.
- After using a fixture. If the smell shows up after you flush a toilet, it could point to a bad toilet seal. If your basement has an ejector pit, air gets pushed out of the pit as it fills, so if the lid isn’t sealed tightly, odors can escape each time it cycles.
- On windy days. Strong winds can blow across or into the vent pipe on your roof, pushing sewer gases back down into your home.
- Certain times of the day. Think about your routine before you notice the odor. If you shower, brush your teeth, and flush the toilet right before it appears, those fixtures may be leading you straight to the source.
When our professional plumbers at Baethke investigate an odor, we walk through these details with you step by step. Every home is different, and knowing where and when you smell it helps us find the cause faster.
Stop the Sewer Smell in Your Chicago Home
A sewer smell in your house usually comes from a dry drain trap in a floor drain, laundry sink, or rarely used shower. Other common causes include a bad toilet seal, a poorly sealed ejector pit lid, corroded vent pipes, or an open pipe left behind after a renovation.
The good news is that many sewer odors have simple fixes, and the rest can be found quickly with the right questions. Paying attention to where and when you smell it is the first step toward getting rid of it for good.
Our recommendation is to start by running water through any drains or fixtures that don’t get used often. If the smell comes back, or you can’t find the source, don’t ignore it. A lingering odor is your plumbing’s way of telling you something needs attention.
For 33 years, Chicago homeowners have relied on Baethke Plumbing to find and fix the problems others miss. Our licensed plumbers will track down the source of your sewer smell, explain what’s causing it, and share upfront pricing before any repair begins.
About the author: John Baethke
Quick Answers About Sewer Smells
What causes a sewer smell in a house?
The most common cause is a dried-out drain trap, usually in a floor drain, basement shower, or guest bathroom that doesn’t get used often. Other causes include a worn toilet wax seal, an unsealed ejector pit lid, and cracked or corroded vent pipes. Where the smell is strongest is the best clue to which one you’re dealing with.
Can a sewer smell come from my washing machine?
Yes. A washing machine drains into a pipe called a standpipe, which has its own trap. If that trap dries out, or the drain hose is pushed too far down into the standpipe, sewer gas can escape into your laundry room. A smell that’s strongest behind the washer, especially after a load drains, points to this cause.
Can I get rid of a sewer smell myself?
Sometimes. If the smell comes from a drain that rarely gets used, pour a gallon of water into it to refill the trap. For floor drains that dry out often, adding a tablespoon of mineral oil on top of the water slows evaporation. If the smell comes back within a few days, is strongest around a toilet, or seems to come from a wall or ceiling, it’s time to call a plumber.
Should I call a plumber or the city about a sewer smell?
It depends on where the smell is. If it’s inside your home, call a plumber, since the cause is almost always in your own drains, toilets, or vent pipes. If the smell is coming from a storm drain, catch basin, or manhole on the street or in the alley, report it to the City of Chicago by calling 311.
How much does it cost to fix a sewer smell?
The cost depends on the cause. Refilling a dry trap costs nothing, and replacing a toilet wax seal or resealing an ejector pit lid is typically a small repair costing $130 to $500. Leaking vent pipes inside walls cost the most, since the wall may need to be opened, and a smoke test may be needed first to find the leak, which could cost $750 to $1,750.
