Why That Smell Keeps Coming Back
An intermittent sewage smell in house can be one of the most frustrating plumbing problems a homeowner faces. The smell appears, you search for it, and by the time you’re ready to investigate, it’s gone. Then it returns days or weeks later.
Quick Answer: Common Causes of Intermittent Sewage Smells
- Dry P-Traps – Water evaporates from unused drains, breaking the seal against sewer gas
- Blocked Plumbing Vents – Clogs in roof vents create pressure issues that pull odors inside
- Faulty Toilet Seals – Worn wax rings allow sewer gas to escape around the toilet base
- Main Sewer Line Issues – Tree roots, cracks, or blockages in your main line cause intermittent backup odors
You’re not imagining it. That rotten egg smell is real, and it’s trying to tell you something about your plumbing system.
Here in Winston-Salem and throughout the Triad, we see this issue often in older homes with cast iron or clay pipes. Aggressive tree roots love our clay soil and find their way into pipes through the smallest cracks. Sometimes it’s a simple fix like refilling a dry P-trap. Other times, it’s a sign your main sewer line needs attention.
The good news is that finding the source is straightforward once you know where to look. This guide will walk you through the detective work, help you understand what’s happening in your plumbing, and show you when a simple fix will work versus when you need professional help.
Many homeowners can solve minor smell issues themselves. For bigger problems, modern camera inspections can help pinpoint the issue without any digging.
Who This Guide Is For
This guide is for any homeowner who has experienced that puzzling, on-again, off-again sewage odor. You might be dealing with a smell that’s only present at certain times of the day, after heavy rain, or when you return home after a vacation. Whether you live in an older home in Ardmore or a newer build in Clemmons, understanding these common causes and solutions can save you stress, time, and potential repair costs. We’ll help you decode the mystery and take the right steps toward a fresher, safer home.
What Causes an Intermittent Sewage Smell in the House?
Most of the time, an intermittent sewage smell in house comes from something straightforward in your plumbing—not the nightmare scenario you might be imagining. Before you worry about tearing up your yard or spending thousands on repairs, let’s walk through what’s usually happening behind the scenes.
Your home’s plumbing system has several built-in barriers designed to keep sewer gas where it belongs: outside your living space. When you catch that telltale rotten egg smell that appears and vanishes without warning, it means one of those barriers has failed. Understanding which one is the key to getting rid of the smell for good.
Dry P-Traps are the most common culprit we see in Winston-Salem homes. Every single drain in your house—sinks, showers, floor drains—has a U-shaped pipe underneath called a P-trap. It holds a small pool of water that acts like a plug, blocking sewer gas from rising up through the drain and into your home. It’s simple, neat, and it works—as long as that water stays there.
Here’s where the problem starts: if you have a guest bathroom that sits empty for weeks, a basement floor drain you never think about, or a utility sink you rarely use, the water in those P-traps slowly evaporates. Once it’s gone, there’s nothing stopping sewer gas from drifting up through the drain. This is why you might notice the smell after returning from vacation or in rooms you don’t use often. The fix can be as simple as pouring water down those forgotten drains.
Dirty drains and biofilm buildup create a different kind of problem, but one that can smell just as bad. Over time, soap scum, hair, food particles, and other organic matter accumulate inside your drain pipes. This creates a slimy coating called biofilm—a breeding ground for bacteria that produces foul odors as it breaks down. The smell from biofilm isn’t technically sewer gas, but it can mimic it closely enough to cause real confusion. You’ll often notice it getting stronger when water runs through the drain, stirring up the buildup, or on humid days when air circulation is poor.
A faulty toilet seal is another common source of intermittent sewer smells, especially in bathrooms. Your toilet sits on a wax ring that creates an airtight seal between the base of the toilet and the floor drain. This seal does double duty: it prevents water leaks and blocks sewer gas from escaping. Over the years, that wax ring can dry out, crack, or shift—particularly if the toilet becomes loose or gets bumped. When the seal fails, sewer gas leaks out from around the base of the toilet. You might notice the smell is strongest right after flushing, when pressure changes push more gas through the compromised seal. If your toilet rocks even slightly when you sit on it, or if you see water stains around the base, a failed wax ring is likely your problem.
Blocked plumbing vents are less obvious but surprisingly common, especially here in the Triad where falling leaves, bird nests, and winter ice can all cause trouble. Your plumbing system has vent pipes—usually extending through your roof—that serve two critical purposes. They release sewer gas safely outside, and they regulate air pressure throughout your drain system. When a vent gets blocked, it can’t do either job properly. The result is negative pressure in your drain lines, which can actually siphon water out of your P-traps or pull sewer gas backward into your home. Blocked vents often announce themselves with slow drains and gurgling sounds from toilets and sinks.
Your 3-Step Smell Detective Checklist:
Refresh Your Drains: Pour a half-gallon of water down every drain in your house, especially ones you rarely use—floor drains, basement sinks, guest bathrooms, utility rooms. This refills any dry P-traps and can solve the problem.
Follow Your Nose: Try to pinpoint where the smell is strongest. Close the doors to each room for a few hours, then open them one at a time. The room with the strongest odor is your starting point for investigation.
Listen for Gurgles: Flush your toilets and run water in your sinks while listening carefully. If you hear gurgling from drains or toilets that aren’t actively in use, you’re likely dealing with a venting issue or a partial clog somewhere in the system.
These simple checks can give you valuable information about what’s happening in your plumbing—and whether you need to dig deeper.
How to Diagnose the Source: A Homeowner’s Walkthrough
Now that you know the common causes, you can play detective. A little investigation can often lead you right to the source of the smell.
Start by isolating the smell. Close the doors to each bathroom and the basement for a few hours. Then open them one by one to see which room has the strongest odor. This simple step helps you narrow your search considerably.
If the smell is isolated to one area, you’re likely dealing with a localized issue like a dry P-trap or a faulty fixture seal. These can often be straightforward to fix. But if the odor is more widespread throughout your home, it might point to a main sewer line or vent stack problem—something that requires a deeper look.
Simple Fixes for an Intermittent Sewage Smell in House
A good first step is to pour water into unused drains. As we discussed earlier, if the intermittent sewage smell in house disappears after you’ve refilled the P-trap, you’ve likely solved it. The water barrier is restored, and the sewer gas can’t escape.
For a dirty drain with biofilm buildup, a gentle cleaning with baking soda and vinegar can often clear out smelly debris. Pour a cup of baking soda down the drain, followed by a cup of white vinegar. Let it sit for about 30 minutes while the mixture fizzes and works through the buildup, then flush with hot water. This approach can help break down biofilm and eliminate odors without harsh chemicals that might damage your pipes.
If the smell returns after a few days, the problem might not be a simple dry trap. That’s when it’s time to look a little deeper.
The Toilet as a Source of an Intermittent Sewage Smell in House
Your toilet might be the culprit, and there’s a simple test. Gently try to rock your toilet from side to side. If it moves at all, the wax ring has likely failed, or the toilet bolts have loosened over time. Either way, the seal isn’t doing its job anymore.
A persistent smell that’s strongest around the base of the toilet is another key sign that the seal needs to be replaced. You might also notice water stains on the floor near the base or a damp feeling around the toilet after flushing. These are all telltale signs of a compromised wax ring.
While replacing a wax ring can be a DIY project for some homeowners, it requires careful handling and proper re-sealing to prevent future issues. If you’re not comfortable with the process, it’s worth calling in a professional to ensure it’s done correctly.
We know how unsettling a mysterious smell can be in your home. Finding the source is the first step toward peace of mind. If these simple checks don’t solve it, the problem might be deeper in your plumbing system, but don’t worry—even bigger issues have straightforward solutions.
Need help? Call The Pipe Boss for trenchless pipe repair in Winston-Salem. We offer camera inspections and written estimates.
When the Smell Signals a Bigger Issue: Your Main Sewer Line
If the smell is present in multiple drains, you notice slow drainage throughout the house, or you’ve had a Sewer Line Back Up, the issue may be in your main sewer line. This is the single pipe that carries all of your home’s wastewater out to the municipal sewer system. When something goes wrong here, it affects your entire home—and often shows up as an intermittent sewage smell in house that seems to come and go, depending on how much water you’re using and what’s happening outside.
The tricky thing about main line problems is that they don’t always announce themselves with a dramatic backup. Sometimes the first sign is just that persistent smell that appears after you do laundry or when the weather changes. You might notice the smell gets stronger when multiple people shower in the morning, or after a rainstorm. These patterns are clues that your main line is struggling.
Common Culprits in Winston-Salem Homes:
For homeowners in Winston-Salem, Greensboro, and throughout the Triad, tree root intrusion is one of the most common causes of sewer line damage we see. Our clay soil causes pipes to shift and settle over time, creating tiny cracks or loose joints. Tree roots are remarkably persistent—they’re drawn to the moisture and nutrients inside your sewer line, and once they find even a hairline crack, they’ll grow right inside. As the roots expand, they create blockages and structural damage. The smell might be intermittent because waste builds up behind the roots, then slowly clears, or because pressure changes in the line push gas back into your home at certain times. This is especially common in older neighborhoods like Ardmore, where mature trees and aging pipes exist side by side.
Pipe age and corrosion are another reality for many Triad homeowners. If your home was built before the 1980s, there’s a good chance your sewer line is made of cast iron or clay. These materials were the standard for decades, but they don’t last forever. Cast iron corrodes from the inside out. Clay pipes can crack or separate at the joints. Over time, these pipes develop what we call “bellies”—sags where waste and water collect instead of flowing freely. They can also develop cracks or even partial collapses. All of these issues trap waste, create blockages, and allow sewer gas to escape into your home. If you’re dealing with this, you’re likely looking at a Winston Salem Sewer Line Repair to restore proper flow and help eliminate those odors.
Main line clogs develop slowly, often over years. Despite what the package says, “flushable” wipes don’t break down like toilet paper. Grease hardens inside pipes. Hair, soap residue, and other debris accumulate. Eventually, all of this creates a stubborn blockage that restricts the flow of wastewater. When your main line is partially blocked, waste backs up into your home’s drains and pushes sewer gas backward into your fixtures. You might notice slow drains across multiple fixtures, gurgling sounds from toilets or sinks that aren’t in use, or that intermittent sewage smell in house that seems to move around. This kind of clog needs a professional Clogged Sewer Line Fix to clear the line and restore normal drainage.
A Modern Solution:
A professional Sewer Drain Camera Inspection in Winston-Salem allows us to see what’s happening inside your pipes. We insert a high-resolution camera on a flexible rod directly into your sewer line through a cleanout or drain. This lets us see the location and nature of roots, cracks, blockages, or pipe deterioration—all without any digging. You can see what we see on a monitor in real time.
Instead of guessing where the problem is, a camera inspection helps us identify the issue before we start. We can show you the roots growing through a joint, the crack in a cast iron pipe, or the grease buildup narrowing your line. This clarity means we can recommend an effective and less disruptive solution for your specific situation, whether that’s trenchless pipe lining, pipe bursting, or targeted repairs. For many homeowners, this inspection can bring peace of mind by identifying the cause of the mysterious smell.
If the smell keeps coming back after checking traps and vents, the problem may be in your main sewer line. A sewer camera inspection is the fastest way to find cracks, root intrusion, or bellied sections that trap waste and release gas into your home. If the camera reveals damage, we offer several sewer line repair options depending on the type and location of the problem.
Understanding Sewer Gas and Why You Shouldn’t Ignore It
That familiar “rotten egg” smell you’re dealing with? That’s mostly hydrogen sulfide, a natural byproduct of decomposing waste in your sewer system. While catching an occasional whiff is mostly just unpleasant, it’s important to understand that an intermittent sewage smell in house isn’t just a nuisance—it’s your plumbing system trying to tell you something important.
What is Sewer Gas?: Sewer gas is actually a mixture of several gases produced by decomposing waste. The main culprits are hydrogen sulfide (that rotten egg smell), ammonia, carbon dioxide, and methane. Your home’s plumbing system is designed to keep these gases contained and away from your living spaces. Every drain has a water-filled P-trap, and your vent pipes direct gases safely outside through your roof. When you smell sewer gas inside your home, it means one of these protective barriers has failed.
Potential Health Risks: While the occasional whiff probably won’t cause serious harm, prolonged exposure to sewer gas can lead to real health concerns. Hydrogen sulfide can irritate your eyes, nose, and throat, and many homeowners report experiencing headaches, dizziness, and nausea when exposed to higher concentrations. Methane, though it doesn’t smell, is another concern—it’s highly flammable and can displace oxygen in enclosed spaces. The smell itself is actually your body’s early warning system, alerting you that something in your plumbing needs attention before it becomes a bigger problem.
It’s a Warning, Not Just a Smell: An intermittent sewage smell in house is your plumbing system’s way of waving a red flag. That small crack in your sewer line or that dry P-trap might seem minor now, but ignoring it can allow a manageable issue to grow into something more serious. We’ve seen simple problems—like a simple toilet seal replacement—turn into major Sewer Line Back Up situations that cause significant property damage. Addressing these warning signs early can help protect your family’s health and your home’s integrity.
A persistent smell means it’s time for a professional look. Have questions? Call The Pipe Boss for sewer line repair.
FAQs
Why does the sewage smell get worse when it rains or during certain weather?
Heavy rain is one of the most common triggers for an intermittent sewage smell in house. When the ground around your sewer line becomes saturated, it can’t absorb gases the way it normally does. This increased pressure sometimes pushes sewer gas back into your home through any weak spots—like a compromised seal, a crack in a pipe, or a partially blocked vent.
Weather changes also affect your plumbing in less obvious ways. Shifts in barometric pressure, which happen when storms move through the Triad, can alter the airflow in your plumbing vents. This pressure change can make odors that were barely noticeable suddenly become much stronger. On the flip side, dry weather can cause the water in seldom-used P-traps to evaporate faster, breaking that protective seal and allowing gas to escape into your home.
Can I just use air fresheners or pour something down the drain to get rid of the smell?
We understand the temptation to reach for an air freshener or a bottle of drain cleaner when that smell hits. Air fresheners might make your home smell better for a few hours, but they’re only masking the problem—not solving it. The source of the odor is still there, and it will return.
Pouring harsh chemical drain cleaners down your pipes can actually make things worse. These products are especially damaging to older cast iron and clay pipes common in Winston-Salem and throughout the Triad. They can corrode pipes, weaken seals, and even create new leaks without addressing the root cause of the smell. A better approach is to find and fix the actual source, which can lead to a more permanent solution and protect your plumbing system.
How do I know if I can fix it myself or if I need to call a plumber?
If you pour a half-gallon of water down an unused drain and the smell disappears, you may have fixed the issue. A dry P-trap is a plumbing problem many homeowners can solve on their own. Similarly, if a gentle cleaning of a drain with baking soda and vinegar clears up the odor, you’ve handled it.
However, if the smell persists after you’ve tried these simple fixes, if it’s affecting multiple drains or rooms in your house, or if you’re experiencing slow drainage and gurgling sounds, it’s time to call a professional. These are signs of a deeper issue in your main sewer line or vent system. Any visible sewage backup, water pooling around fixtures, or leaks around pipes requires professional help, as these situations can escalate and cause damage to your home.
What does a professional sewer inspection involve?
A professional inspection is typically non-invasive. At The Pipe Boss, we use a high-resolution camera mounted on a flexible rod for our Sewer Drain Camera Inspection in Winston-Salem. We guide this camera through your sewer line, starting from an access point like a cleanout or a drain opening.
As the camera travels through your pipes, we can see the pipe’s interior in real time—tree roots breaking through joints, cracks in aging cast iron or clay pipes, blockages from grease or debris, or sections of pipe that have collapsed or developed bellies. This no-dig diagnosis shows us what may be wrong, where it’s located, and how severe the problem is. With a clearer picture, we can create a plan to fix the issue. This reduces guesswork.
How can I prevent sewage smells in the future?
Prevention is often simpler than you might think. An important habit is to regularly run water in every drain in your home, especially those in guest bathrooms, utility sinks, and basement floor drains. Even just running the water for a minute every few weeks keeps the P-traps full and maintains that protective water seal against sewer gas.
Be mindful of what goes down your drains. Never pour grease or cooking oil down the kitchen sink—it solidifies in your pipes and traps other debris. Coffee grounds, “flushable” wipes, and feminine hygiene products should go in the trash, not the toilet. Only human waste and toilet paper belong in your sewer line.
If you have large, mature trees on your property—especially common in neighborhoods throughout Winston-Salem, Lewisville, and Kernersville—consider scheduling a periodic camera inspection. Tree roots are aggressive in our clay soil, and catching root intrusion early, before it causes a blockage or a crack, can save you from a more significant repair down the road. A little prevention goes a long way toward keeping your home fresh and your plumbing system healthy.
Your Next Steps to a Fresher, Safer Home
You’ve taken the right step by learning what could be causing that intermittent sewage smell in house. Whether it’s a simple dry P-trap you can fix in five minutes or a sign of a deeper issue in your sewer line, you now have a clear path forward. You don’t have to live with the worry or the unpleasant odor.
Most homeowners who experience these smells feel a mix of frustration and uncertainty. You might be wondering if you’re dealing with something simple or if there’s a bigger problem lurking beneath your yard. That’s exactly why we’ve walked you through the detective work in this guide—to give you the knowledge and confidence to understand what’s happening in your home.
If you’ve tried the simple fixes—pouring water down unused drains, checking for loose toilets, cleaning out smelly biofilm—and the smell persists, it’s time to call in a professional. At The Pipe Boss, we’ve seen every kind of sewer line issue that Winston-Salem and Triad homes can throw at us. We know the aging cast iron pipes in Ardmore, the aggressive tree roots in Clemmons, and the clay soil challenges throughout Forsyth County.
We believe in providing long-term solutions, not temporary fixes. Our trenchless repair methods and camera inspections are designed to address your sewer line problems, with minimal disruption to your yard. We’ll show you what we find, explain your options, and provide a written estimate before we start any work.
If you’re tired of the smell and ready for a solution, we’re here to help. Need help? Call The Pipe Boss for trenchless pipe repair in Winston-Salem. We offer camera inspections and written estimates.