If you own a home in the Greater Seattle area and you have mature trees on your property, there's a good chance your sewer line has been — or will be — affected by root intrusion.

It's one of the most common sewer problems in the Pacific Northwest, and it catches homeowners off guard because the damage happens slowly, underground, completely out of sight.

Here's what to watch for, and what to do about it.

Why Roots and Sewer Lines Don't Get Along

This part is straightforward biology. Tree roots grow toward water and nutrients. Your sewer line is full of both.

Even a tiny crack or loose joint in an underground pipe releases moisture into the surrounding soil. Roots detect that moisture and grow toward it. Once they find the opening, they enter the pipe — and they don't stop. Inside the pipe, they have unlimited water and nutrients, so they grow aggressively. A hair-thin root can become a dense blockage in a matter of months.

Why This Is Especially Common in the Seattle Area

A few factors make the Greater Seattle metro a hotspot for root intrusion:

We have a lot of trees. Seattle has some of the most extensive urban tree coverage in the country. Mature trees have root systems that can extend well beyond their visible canopy.
Our soil stays moist. The Pacific Northwest climate means roots don't have to dig deep for water. They grow laterally — right through the zone where sewer pipes are typically buried.
Many homes have older pipes. Homes built in the 1950s through 1970s across Seattle, Bellevue, Kirkland, Redmond, and Edmonds often have clay or cast iron sewer pipes. These materials develop cracks and joint separations as they age — exactly the kind of openings roots exploit.

Some tree species are more aggressive than others. Willows, poplars, maples, and cottonwoods are well-known for invasive root systems. But in reality, any mature tree within range of your sewer line can be a problem if the pipe has vulnerabilities.

How to Tell If Roots Are Affecting Your Sewer Line

Root intrusion doesn't happen overnight. The symptoms build over time, which means most homeowners don't notice until the problem is well-established. Here's the progression:

Early signs (easy to dismiss):

Drains seem a little slower than usual — not dramatically, but noticeably
Occasional gurgling from a toilet after flushing
A toilet that takes an extra moment to drain fully

Growing problem (harder to ignore):

Multiple drains in the house are slow — kitchen, bathroom, and laundry
Clogs that come back within weeks of being snaked
Gurgling sounds when running the washing machine or dishwasher

Urgent (don't wait):

Sewage backing up through floor drains or the lowest fixtures in the house
Sewage smell in the yard, especially in one concentrated area
Soft or sunken spots in the lawn above where the sewer line runs

If you're experiencing anything in the "growing problem" or "urgent" category, a sewer camera inspection is the smartest next step. It costs a fraction of an emergency repair and tells you exactly what you're dealing with.

What to Ask a Sewer Contractor About Root Intrusion

If you suspect root intrusion and call a professional, here are the right questions to ask:

"Can you show me the camera footage?" — A good contractor will walk you through what the camera sees inside your pipe. You should be able to see the roots yourself and understand the extent of the problem.

"Is this a one-time cleaning, or do I need a longer-term fix?" — Clearing roots out of a pipe solves the immediate blockage, but if the cracks and openings aren't repaired, the roots will grow back. Ask whether a repair or pipe upgrade makes sense for your situation.

"What are my options, and what does each one cost?" — Root problems range from minor (a single root entry point) to severe (roots throughout the entire pipe). The right solution depends on the severity, and you should understand all your options before committing.

"How can I prevent this from happening again?" — A knowledgeable contractor should be able to advise you on preventative measures — whether that's regular inspections, periodic cleaning, or pipe upgrades.

When to Get an Inspection

A good rule of thumb for Seattle-area homeowners:

If your home is 20+ years old and has mature trees on the property — get a sewer camera inspection, even if you're not experiencing symptoms. It's inexpensive peace of mind.
If you're experiencing any of the symptoms above — get an inspection soon. The longer you wait, the more expensive the fix becomes.
If you're buying a home — always request a sewer scope as part of your due diligence (more on that in our home-buying guide).

Seattle Select Sewers Can Help

We've been diagnosing and resolving root intrusion problems across the Greater Seattle area since 2005. We serve homeowners in Seattle, Bellevue, Kirkland, Redmond, Everett, Edmonds, Issaquah, Burien, and Bothell.

Our approach: inspect first, show you what we find, explain your options, and give you an honest recommendation. No pressure, no upselling.

Call 425-531-4847 or visit seattleselectsewers.com to schedule a camera inspection and find out what's going on in your sewer line.

If you have questions, please do not hesitate to reach out to us at (425) 531-4847 or contact@seattleselectsewers.com. We're always happy to discuss our services, issues you may be facing and be a resource.