Tree Roots in Sewer Lines: The Number One Cause of Drain Blockages in Older Homes

Older homes have their charm—solid craftsmanship, architectural character, and mature landscaping. But those beautiful, sprawling trees that surround them can hide a costly issue below the surface: invasive roots. In many aging neighborhoods, root intrusion is the leading cause of persistent sewer line clogs. If you’re living in a house built before the 1980s and noticing repeated drainage issues, there’s a high likelihood that tree roots are the culprit.

When dealing with these types of problems, fast action is key. That’s where professional sewer line repair & replacement in Seattle by Ben’s Plumbing can make all the difference. Attempting to manage root-related sewer issues without the right tools or experience often leads to more damage—and bigger repair bills.

Why Tree Roots Invade Sewer Lines

Tree roots are naturally drawn to moisture and nutrients. Sewer pipes, especially older clay or concrete ones, provide both. Over time, microscopic cracks or poorly sealed joints in these pipes create the perfect entry points for roots to sneak inside. Once inside, roots quickly expand, catching debris, creating blockages, and sometimes even causing the pipe to collapse.

Even species known for slow growth above ground—such as maples or elms—can develop aggressive underground root systems. These roots don’t grow toward sewer lines because they’re “looking” for waste; they grow in search of water. And once they find a steady source, they don’t let go easily.

Signs You Might Have Root Intrusion

Root intrusion isn’t always immediately obvious, but it often begins with warning signs that escalate over time. Here are some indicators your home may be affected:

• Frequent slow drains: Especially in toilets, bathtubs, or basement drains.
• Gurgling sounds: Air pockets created by obstructions often produce this noise.
• Multiple clogs at once: If more than one fixture is backing up, the issue likely lies in the main sewer line.
• Unpleasant odors: Foul smells coming from drains may signal waste trapped behind a root blockage.
• Sudden wet patches in the yard: A damp area above your sewer line may indicate a break caused by root pressure.

Modern Solutions for Root-Blocked Sewer Lines

There are two primary ways to address tree root problems: mechanical removal and structural repair. In some cases, a combination of both is necessary.

1. Mechanical Root Removal

Professional plumbers often begin by clearing the blockage using a motorized auger or a hydro jet. A hydro jetter uses high-pressure water to cut through root masses and flush them out of the pipe. This method not only removes the roots but also cleans the pipe walls, reducing the chance of new root growth in the short term.

However, cutting roots is not a long-term fix if the pipe remains damaged. Left unaddressed, roots can grow back and re-block the line—sometimes in just a few months.

2. Sewer Line Repair or Replacement

When roots have cracked or dislocated the pipe, structural repair is essential. Trenchless methods, such as pipe bursting or cured-in-place pipe (CIPP) relining, have made the process much less invasive than in years past. These techniques allow plumbers to restore or replace the pipe without digging up your entire yard.

Here’s what these modern techniques involve:

• Pipe Bursting: The old pipe is broken apart as a new pipe is pulled into place.
• CIPP Relining: A flexible liner soaked in resin is inserted and cured in place, forming a new pipe within the damaged one.

Both methods create a seamless pipe that roots can’t penetrate, restoring your system’s function and reducing the risk of future infiltration.

DIY Fixes Are Not Enough

While some homeowners attempt to treat root problems using chemical root killers or store-bought augers, these temporary fixes rarely solve the underlying damage. Overuse of chemical treatments can harm the environment, and mechanical methods done incorrectly can crack already fragile pipes.

In older homes, sewer lines may be decades past their intended lifespan. Attempting to manage these systems without proper diagnostic tools, like a sewer inspection camera, often leads to misdiagnosis—or worse, costly structural damage.

Why It’s Best to Call the Professionals

Certified plumbing technicians bring more than tools—they bring experience, training, and the ability to evaluate the full picture. They can identify the exact location of root intrusion using video inspection, determine the extent of pipe damage, and recommend a solution tailored to your specific system and soil conditions.

Professional plumbers can also advise on preventative steps, such as removing invasive tree species or installing root barriers, to keep your system protected for years to come.

Preventing Root Intrusion in the Future

While you can’t always control what trees your neighbor plants or how roots grow, you can take a few smart steps to reduce risk:

• Know where your sewer line runs and avoid planting trees within 10–15 feet of it.
• Schedule regular video inspections, especially if your home is more than 30 years old.
• Address slow drains early—don’t wait for a full blockage.
• Replace outdated clay or cast-iron pipes with PVC or other root-resistant materials.

Tree roots in sewer lines are one of the most common—and most preventable—causes of recurring blockages in older homes. When caught early and handled professionally, the damage can be contained before it turns into a full-blown plumbing disaster.