You catch a whiff of something foul — rotten eggs, sewage, something damp and sour — and you can't figure out where it's coming from. You check the toilet. Sniff the sink. Walk room to room. Nothing obvious. And then it's gone. Or maybe it's not gone. Either way, it's back the next morning.
If this sounds familiar, you're not imagining it — and you're not alone. As expert plumbers serving High Point and Guilford County, this is one of the most common calls we get. The frustrating part is that a sewer smell in your home can come from half a dozen different places, and most of them look perfectly normal on the surface.
This guide walks through every likely cause, from the easy five-minute fixes to the ones that need a professional. We'll start with the most common culprit and work our way down.
The Short Answer: A Sewer Smell Usually Means Your Plumbing System Has a Breach Somewhere
Every drain in your home — every sink, tub, toilet, and floor drain — is designed to keep sewer gases out of your living space. When you smell sewage, something in that system has failed. The question is which part.
Sewer gas is a mix of hydrogen sulfide, methane, ammonia, and carbon dioxide. The rotten egg smell is hydrogen sulfide. Beyond being unpleasant, sewer gas in high concentrations can cause headaches, nausea, and in extreme cases (confined spaces, prolonged exposure) is genuinely hazardous. In most homes, the concentration that reaches living areas is low — but that doesn't mean you should ignore it.
Here are the eight most common causes, in order of how frequently we see them.
1. A Dry P-Trap — The Most Common Culprit
What it is: The P-trap is the curved section of pipe directly beneath every sink, tub, and shower drain. That curve holds a small amount of water — and that water is the seal blocking sewer gases from traveling back up through the drain into your home.
When a drain goes unused for an extended period, that water evaporates. The seal is gone. Sewer gas rises straight through the open drain.
Where this happens most: Guest bathrooms, basement floor drains, utility sinks, spare bedroom sinks — anywhere that doesn't get used regularly. In High Point's older two-story homes with a half bath or utility sink in the basement, this is extremely common.
The fix: Run water down every drain in your home. Run the bathroom sink, the tub, the shower. Pour a cup of water down any floor drain you haven't used recently. If the smell goes away within a few hours, this was your problem. Add a tablespoon of cooking oil to infrequently used drains — the oil floats on the water and slows evaporation.
One caveat: If the smell returns quickly — within a day or two — the P-trap may have a crack or the connected vent may be the issue. That's a different problem.
2. A Failing Wax Ring on a Toilet
What it is: Every toilet sits on a wax ring — a thick ring of soft wax that creates a watertight, gas-tight seal between the toilet base and the floor flange beneath it. When this seal degrades or breaks, sewer gases escape directly at the base of the toilet.
Signs to look for:
- The smell is strongest in the bathroom, near the floor
- You notice slight movement or rocking when you sit on the toilet
- There's discoloration or soft flooring around the toilet base
- The toilet has been removed and reinstalled at some point (improperly reseated toilets are the most common cause of failed wax rings)
What causes wax rings to fail: Age, a toilet that was improperly installed without proper compression of the wax, a toilet that rocks slightly on an uneven floor (over time this breaks the wax seal), or an unusually high or low floor flange relative to the finished floor height.
The fix: The wax ring needs to be replaced. This requires removing the toilet, scraping out the old wax, inspecting the floor flange for cracks or corrosion, installing a new ring, and resetting the toilet. It's a manageable DIY job for someone comfortable with basic plumbing, but it requires proper technique — an improperly seated toilet will fail the wax ring again within months.
3. A Blocked or Damaged Sewer Vent Stack
What it is: Your plumbing system has a vent pipe — usually 3 to 4 inches in diameter — that runs up through the interior of your home and exits through the roof. This vent does two things: it allows air into the drain system so water flows freely, and it allows sewer gases to escape harmlessly outside rather than back into the house.
When the vent is blocked or damaged, sewer gases have nowhere to go — so they find another way out. Usually through your drains.
What blocks sewer vents:
- Bird nests, leaves, or debris accumulating at the roof opening
- Ice formation over the vent opening during winter freeze events — during sustained below-freezing temperatures in High Point, moisture from the vent can freeze and seal the opening
- A damaged or crushed vent pipe inside the wall
- A vent pipe that was improperly sized or connected during renovation
Signs of a vent problem:
- Gurgling sounds from drains after flushing a toilet or running a sink
- Slow drains throughout the house, not just one fixture
- Smell is intermittent and seems to move around — present in one bathroom, then another
- The smell is worse after heavy rain or extreme cold weather
The fix: A plumber can inspect the vent stack from the roof, clear any blockage, and camera the interior if a structural problem is suspected. A blocked vent from debris is a simple fix. A cracked or separated vent pipe inside a wall requires more involved repair.
4. Biofilm Buildup in Drain Lines
What it is: Over time, organic material — soap residue, hair, grease, toothpaste, skin cells — accumulates on the interior walls of drain pipes and creates a thick layer of biofilm. This material breaks down anaerobically and produces hydrogen sulfide gas. It smells exactly like sewage, even though it's not coming from the sewer line itself.
Where this shows up most: Bathroom sink drains are the most common location. The pop-up stopper mechanism creates a ledge where debris collects. Shower drains are also frequent offenders. In High Point homes with cast iron drain lines — common in homes built before 1970 in neighborhoods like Emerywood and Sherwood Forest — the rough interior surface of older cast iron pipe accumulates buildup faster than smooth PVC.
Signs it's biofilm, not something worse:
- The smell is strongest right at the drain opening
- It smells bad when you run water, not just randomly
- The drain may also be running slowly
The fix: Remove the drain stopper or cover and clean it thoroughly — most of the buildup lives there. For the drain pipe itself, a drain cleaning solution or enzymatic drain treatment can help, but a thorough cleaning with a drain snake or hydro jetting will eliminate it completely. Don't rely on chemical drain cleaners for this — they're hard on older pipes and rarely solve the root problem.
5. A Cracked or Deteriorated Drain Pipe
What it is: If a drain pipe in your home has developed a crack — even a hairline crack — sewer gas can escape through it into the surrounding structure and eventually work its way into your living space. You won't see the crack. The pipe may drain fine. But the gas is getting through.
Who's most at risk in High Point: Homes built before 1970 with original cast iron drain systems. Cast iron is a durable material, but after 50 to 70 years it corrodes from the inside out. The horizontal sections of cast iron pipe — especially in crawl spaces and basements — are prone to developing cracks and holes as the bottom of the pipe rusts through while the top remains intact.
Cast iron drain failures are one of the most common things we see in the Emerywood, Sherwood Forest, and downtown-adjacent neighborhoods of High Point. The pipe holds up for decades, looks fine externally, and then fails from within.
Signs of a cracked drain pipe:
- A persistent smell that doesn't go away after addressing traps and vents
- Smell is stronger in the crawl space, basement, or near interior walls
- Mold or moisture issues in areas adjacent to plumbing runs
- Older home (pre-1970) with original drain system
The fix: A sewer camera inspection can locate cracked pipe in the main line. For interior drain lines in walls and floors, a plumber experienced with older systems can assess and recommend repair or spot replacement. Cast iron that is failing in multiple locations typically warrants whole-house repiping of the drain system — a significant but permanent solution.
6. A Missing or Loose Cleanout Cap
What it is: Your sewer system has cleanout access points — typically a threaded cap at the end of a cleanout pipe — that allow plumbers to access the sewer line for inspection and clearing. These caps are usually located near the foundation exterior, or sometimes in a basement or utility area.
If a cleanout cap is missing, cracked, or was never fully tightened after previous plumbing work, there's an open connection to the sewer with no trap between it and your indoor air.
Where to check: Walk the perimeter of your home's foundation and look for a white PVC or black ABS cap (usually 3 to 4 inches in diameter) set in the ground or just above grade. Also check basements and utility rooms for any capped pipes near floor level.
The fix: A replacement cap costs under $10 at any hardware store. If the fitting itself is cracked, a plumber may need to replace the fitting and cap. This is one of the simplest and most overlooked causes of sewer smell.
7. Sewer Line Problems Underground
What it is: The sewer lateral — the underground pipe that runs from your house to the municipal connection at the street — can develop cracks, root intrusion, or partial blockages that allow sewer gases to migrate back toward the house through the drain system.
This is less common as the sole cause of odor than the issues above, but it becomes relevant when the smell is persistent, no interior cause can be found, or when multiple drains in the home are affected.
High Point's specific risk: The sewer laterals in High Point's older neighborhoods — particularly Emerywood, Sherwood Forest, and the historic corridors along Main Street and Kivett Drive — were originally installed as vitrified clay tile or cast iron. These pipes are 60 to 80 years old. The joints are not sealed; they rely on tight-fitting sections. As soil shifts and the pipe ages, joints open up. Tree roots — the large oaks and maples that give these neighborhoods their character — actively seek out those open joints and grow into the pipe interior.
Root intrusion creates a partial blockage that traps gas and causes intermittent odors and slow drains simultaneously.
Signs the sewer line may be involved:
- Multiple drains running slowly at the same time
- Gurgling from one drain when you flush a toilet elsewhere in the house
- Smell is worst in the basement or lower-level floor drains
- Sewage smell in the yard, particularly in a strip from the house toward the street
- You've had the drain cleaned before and the problem keeps coming back
The diagnostic step: A sewer camera inspection. A waterproof camera is fed through the cleanout into the lateral and records the interior condition in real time. This is the only way to know the actual condition of underground pipe. In High Point, we recommend this for any home over 30 years old that hasn't had a camera inspection, and as a non-negotiable step before purchasing an older home. Camera inspections typically cost $150–$350 in the local market.
8. Intermittent Odor — When the Smell Comes and Goes
An intermittent sewer smell — present some mornings, gone by noon, back after heavy rain — often points to one of these specific scenarios:
Dry trap that refills and dries again: An infrequently used drain's trap refills when you run water elsewhere in the house, then evaporates again. The cycle produces an on-and-off smell.
Vent stack freezing in winter: During cold snaps — and High Point experiences genuine hard freezes several times each winter — the vent stack opening on your roof can partially ice over, reducing the system's ability to exhaust gas outside. The smell typically resolves when temperatures rise. If you notice the smell consistently during cold weather, the vent is worth investigating.
Barometric pressure changes before storms: During low-pressure weather systems, gases that normally exhaust upward through vents can move downward instead. Many homeowners notice a sewage smell before rain. This is a real phenomenon and often indicates the vent system is marginal and needs attention.
Wind-driven backdrafting: On certain wind conditions, outdoor air pressure can push gases back down through the vent stack. This is particularly noticeable in two-story homes where the vent terminates close to the roofline.
When to Call a Plumber
Try these steps yourself first:
- Run water down every drain in the house, especially guest bathrooms, basement drains, and utility sinks
- Check every cleanout cap on the exterior of the house
- Remove and clean sink drain stoppers
- Flush the toilet in every bathroom and note whether the smell is localized to one area
If the smell resolves after these steps, you likely had a dry trap or minor biofilm issue. Keep those infrequently used drains wet going forward.
Call a plumber when:
- The smell persists after running all drains
- You hear gurgling from drains when flushing toilets
- Multiple drains are slow at the same time
- The smell is strongest in the basement or crawl space
- You have an older home (pre-1975) and haven't had the drain system or sewer lateral inspected
- The toilet rocks when you sit on it
- The smell is localized to one bathroom and won't go away
Call a plumber immediately when:
- Sewage is backing up into any drain, tub, or floor drain — this is a health emergency
- The smell is extremely strong and concentrated throughout the house
- Anyone in the home is experiencing headaches or nausea that may be related to sewer gas exposure
Frequently Asked Questions
Why does my house smell like sewer only in the morning?
The most likely explanation is a dry P-trap. At night, your home is closed up and the air inside is still. Gas that accumulates in an empty trap overnight is noticeable when you first enter the space in the morning. Once you run water and open windows, it dissipates. Run water down every drain in your home — especially ones you don't use daily. If the smell is consistent every morning in a specific room, focus on the least-used drain in that room first.
My house smells like sewer after it rains — why?
Rain and low barometric pressure can push gases that would normally exit your roof vent back down through the drain system. Rain also saturates soil around sewer laterals, which can force gas through cracks or loose joints in underground pipe back toward the house. If this happens consistently, it's worth having the sewer lateral camera-inspected — rain-triggered odor is a reliable indicator of a pipe with compromised joints.
I only smell sewage in one bathroom — what does that mean?
A localized smell in one bathroom narrows the problem significantly. First, check whether the toilet rocks at all — even slight movement indicates a failed wax ring. Next, run water in every fixture in that bathroom and see if the smell dissipates (dry trap). If neither resolves it, the vent stack serving that bathroom may be partially blocked, or there's a cracked drain connection behind the wall.
How much does it cost to fix a sewer smell in High Point?
It depends entirely on the cause. A replacement cleanout cap costs under $20 in parts. A wax ring replacement runs $150–$250 for a plumber. Clearing a blocked vent stack runs $200–$400 depending on roof access. A sewer camera inspection is $150–$350. If the issue is a failing sewer lateral requiring trenchless repair, costs start around $3,000–$6,000. Most sewer smell problems are on the inexpensive end — the key is diagnosing the cause correctly so you're not paying for the wrong repair.
Can sewer gas actually be dangerous?
At the concentrations that typically reach living areas through plumbing breaches, sewer gas causes headaches and nausea in sensitive individuals but is not immediately dangerous. The concern is sustained exposure in a confined space — a basement, crawl space, or small bathroom with poor ventilation. Methane in sewer gas is also flammable at high concentrations. If the smell is extremely strong or anyone in the home is feeling ill, open windows, get some fresh air, and call a plumber. Don't dismiss a persistent strong smell as just a nuisance.
Could the smell be coming from the city sewer main, not my plumbing?
It's possible but uncommon. If neighbors are reporting the same smell, or if the city has been doing sewer work in the area, the municipal main could be the source. Contact High Point Water Resources at (336) 883-3111 to report it. If the smell is isolated to your home, the problem is almost certainly your private plumbing.
My drains seem fine — can I still have a sewer line problem causing the smell?
Yes. A cracked sewer lateral can allow gas to escape without meaningfully restricting flow, especially if the crack is small. Root intrusion often starts as an odor issue months before it becomes a slow-drain issue. This is why a camera inspection is more reliable than drain behavior as a diagnostic tool — by the time drainage is noticeably affected, the pipe damage is already significant.
The Bottom Line
A sewer smell in your High Point home usually has a fixable cause — and often it's a simple one. Start with the basics: run every drain, check every cleanout cap, and clean the drain stoppers in your bathrooms. Many homeowners resolve the problem the same day without a service call.
If the smell persists, or if you have an older home with original cast iron drains or an uninspected sewer lateral, it's worth having a plumber take a look. The cost of a camera inspection is a fraction of what you'll spend ignoring a deteriorating lateral until it backs up into your home.
If you're dealing with a persistent sewer smell in your High Point home and can't locate the source, give us a call. We serve High Point, Archdale, Jamestown, Thomasville, and the surrounding Guilford County area.
Call us at 336-422-7560 — we can usually schedule same-day or next-day appointments for diagnostic calls.
