Common Causes of Sewer Smells in Your House (Denver & Front Range Guide)
Sewer smells in your house can indicate something small like a drain trap that has dried out, or a more serious problem like deep clog in a drain. In Denver, homeowners deal with a few causes that plumbers in wetter parts of the country rarely see.
Denver’s dry air, freezing winters, and the clay and cast iron lines under older neighborhoods add plumbing challenges uncommon in other parts of the country. Understanding the common causes of sewer smells can help you narrow down the source and decide whether it’s a quick fix or a job for a plumber.
Key Takeaways
- Dry P-traps, blocked vent stacks, clogged drains, cracked lines, and failing wax rings are the most common causes of sewer odors in your house.
- Denver’s low humidity and freezing winters create seasonal odor problems that homes in humid climates don’t experience.
- Flushing every drain and refilling floor drain traps can resolve sewage odor problems without a service call.
- If the smell returns after flushing, Sanders & Johnson can perform a camera inspection to locate the problem in your vent stack or sewer line.
What Causes Sewer Smell in a House?
Curious what causes sewer smells in a house? Sewage smells can seep into your home when the barrier between your drain system and your living area fails. Some of the most common culprits include:
- Dry P-traps: When the water in P-traps evaporates after weeks of being unused, in guest bathrooms, basement floor drains, or laundry sinks, sewer gas rises straight up through the open drain.
- Blocked or damaged vent stacks: Birds’ nests, leaves, ice, and other buildup can block the plumbing vent that allows sewer gas to escape, causing it to back up into your living space.
- Clogged drains: Without regular drain cleaning, hair, soap scum, and food waste can build up in your drains, coat the inside of pipes, and rot in place.
- Cracked or leaking sewer lines: A damaged sewer line allows gas to seep up through soil and into your basement or crawlspace, even with no water backing up at all.
- Failed wax ring: When the wax ring seal at the base of your toilet dries out or shifts, gas can escape around the base and spread through the bathroom.
Why Denver Winters Make Sewer Odors Worse
Denver’s cold, dry winters make sewer odors worse by trapping gas that should be venting above your roof. When single-digit temperatures cause the moist air rising through your vent stack to freeze inside the pipe and create a layer of ice that narrows or seals the opening, gas that should be released through your roof gets pushed back down into your house. The warm air rising and escaping through your upper floors makes the problem worse, creating a negative pressure that pulls sewer air through any gap in your drainage system.
The dry winter air also speeds up evaporation. Denver averages around 40% relative humidity in the winter, with some days below 10%, causing trap water that would last over a month in a humid climate to evaporate within a week or two.
Is Sewer Gas Dangerous?
Sewer gas isn’t usually dangerous in the concentrations found in a house, but it still requires attention. It’s a mix of methane, hydrogen sulfide, ammonia, and other gases, and at low levels mostly causes minor symptoms like headaches, nausea, and eye irritation. Being exposed to sewer gas for a longer period or at a higher concentration can cause more serious symptoms and be especially harmful to children and those with respiratory problems.
DIY Checks Before Calling a Plumber
Before calling a plumber for sewage smells, start by running water in every sink, tub, and shower for about a minute to refill the traps. Pouring a couple of quarts of water into the basement and laundry room floor drains and flushing every toilet in the house also restores the seal in fixtures you don’t use often.
Wait a day and see if the smell comes back. If it’s gone, a dry trap was likely the problem and can be prevented with a monthly flush of unused drains.
When to Call a Plumber for Sewer Smells
If the sewage smells in your house linger even after a full round of drain flushing or the odor is coming from your basement or crawlspace, call a plumber. These warning signs often mean the problem is in the vent stack or the sewer line, which require professional diagnosis.
You should also call for help if the odor is paired with slow-running drains throughout your house, low water pressure, or gurgling noises from your fixtures. These symptoms can indicate a main line blockage, which plumbers can diagnose and locate with a camera inspection. Once they can see inside the line, they can help you decide whether you need a cleaning, spot repair, or full line replacement.
Call Sanders & Johnson for Sewer Odor Diagnosis in Denver
If you’re dealing with sewage smells that won’t go away on their own, call Sanders & Johnson for a professional diagnosis. We offer same-day service for sewer and drain problems with no after-hours fees, so you can get answers right away.
You’ll get a photo and short bio of your technician before they arrive, and clear recommendations once we understand where the odor is coming from. Whether you need a simple drain flushing or sewer repair, we’ll outline your options in clear terms so you can make the right decision for your home and budget.
Call us or book online to schedule sewer services in Denver today!
Frequently Asked Questions
Why does my house smell like sewer gas all of a sudden?
A sewer smell that comes on suddenly is often linked to a dried-out trap or blocked vent. If you have a guest bathroom that’s gone unused for weeks, it’s the middle of a hard freeze, or you’ve had an exhaust fan running more often than usual, you’ve likely found your culprit.
Can a cracked sewer line cause a smell without a visible leak or backup?
Cracked sewer lines can cause a smell, even if there’s no visible leak or backup. Gas travels through soil more easily than water does, so you can have a cracked line venting odor into your basement even with your drains running normally.
Why does the smell only happen in winter?
Winter sewage smells are usually caused by frost closure in your vent stack or pressure differences from heating your home. Cold, dry indoor air can also evaporate trap water faster, so several causes can show up when a Front Range cold snap arrives.
How much does it cost to fix a sewer line in Denver?
The cost to fix a sewer line in Denver depends on the length of the run, the depth, and the repair method. Our team always provides an upfront quote before beginning any work, and lays out your options so you can decide which solution makes the most sense for your home.
Do I need a plumber, or can I clear the smell myself?
You can often clear minor sewage smells yourself with a full home drain flushing. If the odor comes back within a day or two, you need a plumber to inspect your vent stack and sewer line.
