If you’ve noticed a foul sewer smell creeping through your home, especially near drains, toilets, or the basement, you’re not alone. Sewer odors are an unpleasant but surprisingly common problem for homeowners in Portland. With our city’s aging infrastructure, wet climate, abundance of mature trees, and large number of historic homes, it’s no surprise that plumbing systems sometimes let us know they need attention, usually with a smell we can’t ignore.
In this post, we’ll walk you through the most common causes of sewer odors, explain why they happen more often in Portland homes, and help you determine when it’s time to bring in a professional plumber.
What Causes Sewer Odors Indoors?
Sewage smells in your house are typically a sign that sewer gases are escaping from somewhere they shouldn’t. A properly functioning plumbing system is designed to trap and safely vent these gases, but when something goes wrong, those smells can enter your living space. Here are the most common culprits:
Dry P-Traps
Every drain in your home has a P-trap. A P-trap is a curved section of pipe designed to hold a small amount of water. That water creates a seal that keeps sewer gases from coming back up the drain. If you have a sink, shower, or floor drain that doesn’t get much use (especially in a basement or guest bathroom), that trap can dry out and lose its seal, allowing odors to escape.
Quick Fix: Pour water down unused drains every few weeks to refill the trap.
Cracked or Damaged Sewer Lines
Many older homes in Portland were built with clay or cast iron sewer pipes, which are more prone to cracking over time. Shifting soil, tree root intrusion, or corrosion can cause breaks in the line, allowing sewer gas to escape underground or even back into your home if pressure builds up.
This issue often comes with other symptoms like slow drains, soggy patches in your yard, or recurring backups.
Blocked Plumbing Vents
Your plumbing system relies on vertical vent pipes—usually exiting through the roof—to equalize pressure and safely release sewer gases outside. If one of these vents becomes blocked by leaves, bird nests, or ice during Portland’s colder months, those gases may get pushed back into your home through the drains.
Worn Toilet Seals
The wax ring that seals your toilet to the floor can wear out or become loose over time. When that happens, it may allow sewer gas to seep into the bathroom, especially when the toilet is flushed or pressure changes in the plumbing system.
Why Sewer Odors Are a Bigger Deal Than You Think
Sewer gas isn’t just a nuisance—it can pose real health risks. Hydrogen sulfide, the gas responsible for the “rotten egg” smell, can cause headaches, dizziness, and even respiratory issues at high levels. More often, persistent odors indicate hidden leaks, mold growth, or other problems that can worsen over time and lead to costly damage.
How to Diagnose the Source of the Smell
Here are a few steps you can take if you notice a persistent odor:
- Check for dry or unused drains.
- Sniff around toilets, sinks, and baseboards to localize the source.
- Listen for unusual gurgling sounds when water drains.
- Look for signs of moisture or discoloration around plumbing fixtures.
If the problem isn’t obvious or easy to fix, it may require professional tools like a smoke test or video camera inspection to pinpoint the issue.
When to Call a Professional Plumber in Portland
Don’t wait too long to bring in an expert if:
- The smell is getting worse or spreading.
- You’ve tried basic fixes, but the odor keeps returning.
- You notice slow drains, gurgling, or signs of water damage.
- You suspect a cracked or collapsed sewer line.
At Mr. Rooter Plumbing, we’ve helped homeowners across the metro area—from Wilsonville to North Portland—quickly identify and resolve sewer odor issues. We understand the plumbing challenges that come with older homes, clay pipes, and heavy rainfall, and we have the tools and experience to handle it all.
Final Tips for Preventing Future Odors
- Run water through all your drains regularly to keep traps from drying out.
- Schedule seasonal plumbing maintenance, especially before Portland’s rainy season.
- Consider a video inspection of your main line every few years, especially if your home is more than 40 years old.
- Don’t ignore slow drains—they’re often the first warning sign of a deeper issue.
