Quick answer
Tree roots usually enter a sewer line through existing cracks or loose joints, drawn by moisture and nutrients. Common signs are slow drains, gurgling toilets and backups. A camera inspection confirms roots and shows the pipe's condition. Clearing roots is often temporary because they tend to regrow, so damaged pipe may need spot repair, relining or replacement. A plumber can recommend what fits.
Signs roots may be in your sewer line
EPCOR, the water and drainage utility in Edmonton, Alberta, lists several warning signs of root growth in a sewer pipe. They are gurgling toilets, slow-draining sinks, tubs or floor drains, wet spots around floor drains after laundry, and a basement floor drain that backs up. King County, Washington, adds sewer odors to its list of side sewer warning signs.
None of these signs proves roots are the cause. Seattle Public Utilities (SPU) names grease buildup, flushed debris, roots and cracked pipe as common reasons a sewer line has trouble, and the symptoms overlap. That is why the next step is usually a look inside the pipe rather than a guess.
- Gurgling toilets or drains
- Slow drains in more than one fixture
- A floor drain that backs up or gets wet after laundry
- Recurring clogs that keep returning after clearing
- Sewer odors indoors or in the yard
- Sewage overflowing from a drain or fixture: stop using water and treat it as urgent
Why roots get into sewer pipes
EPCOR explains that roots grow toward moisture and nutrients. Warm water in a sewer pipe gives off vapor that escapes into cooler soil, and roots follow it. They push through cracks or joints to reach the water inside, then keep growing and can fill the pipe.
That means roots generally need an opening. SPU says roots grow into cracks or holes, especially in older pipes, and that cracked pipes both leak sewage and invite root damage. The City of Seattle's tree guidance says roots from a tree planted too close can grow into small cracks in water and sewer lines over time. EPCOR adds that older clay and concrete pipes, with more joints, are more vulnerable than PVC, and that roots can travel far during drought and winter in search of water.
The sources are less clear on whether roots can break a sound pipe by themselves. EPCOR says roots can eventually cause a pipe to break or collapse once they are inside, but describes them entering through existing cracks or joints. In practice, a plumber looking at your pipe can tell you whether the pipe was already damaged.
How a camera inspection confirms the problem
SPU says a plumber, drain rooting service or sewer inspector can run a video camera through the pipe to find problems such as grease, roots, debris and cracks. EPCOR likewise notes that a television inspection can confirm root intrusion. The video shows where the roots enter, how much of the pipe they fill, and whether the pipe itself is cracked, offset or collapsing.
That information drives the repair decision. A clear picture of the pipe is also useful when you compare quotes, so it is reasonable to ask for the recording or still images. SPU suggests getting quotes from several companies.
SPU recommends inspecting a side sewer every 8 to 10 years in general, but every 2 to 3 years if large trees or shrubs grow nearby. It also recommends an inspection before buying a home. Inspection timing is a utility recommendation for Seattle, so ask your own city or sewer district if it publishes different guidance.
Clearing roots: what it does and does not do
EPCOR describes mechanical removal, using tools such as augers, root saws and high-pressure flushers, as a way to clear a blockage. It also warns that cutting roots often leads to faster, thicker regrowth. For chemical treatments, it says safe herbicides can slow regrowth for 3 to 5 years.
A University of Washington horticulture library page quotes University of Georgia Extension in a similar way. It says both mechanical removal and copper sulfate products are temporary, and that removing the tree is the permanent solution. The same page says copper sulfate is highly toxic to people and aquatic life and should be checked with the sewer utility to confirm it is permitted in the sewer system. Treat any chemical root product as something to clear with your sewer utility and a plumber first.
The takeaway is that clearing is a reasonable first response to a blockage and a way to buy time, but it does not fix the opening the roots came through. If the camera shows cracks or open joints, expect the roots to return.
Repair, replacement and trenchless options
EPCOR says severely damaged pipes may need repair or replacement, and that old clay tile is especially vulnerable. King County says that if a side sewer has cracks or leaks, owners should plan to replace it eventually and check with their city about permits.
Replacement can be done by digging up the old pipe and installing new pipe. SPU says repairs that do not require digging, such as relining or pipe bursting, are an alternative, and that repairs that require digging are more expensive. It does not say that either approach fits every pipe.
NASSCO, the trade association for pipeline rehabilitation, says trenchless methods either line the existing pipe with a new pipe inside it or replace the old pipe without digging a full trench. Two common ones are cured-in-place pipe lining and pipe bursting.
With cured-in-place lining, a resin-soaked tube is placed in the existing pipe and cured to form a new seamless pipe inside it. NASSCO says it can address cracks, leaks and corrosion, and that lateral lining is a permanent solution against root intrusion, with a minimum life expectancy of 50 years when properly installed. That is a trade body's description of a properly installed lining, so treat it as a best case and ask any contractor what warranty applies.
With pipe bursting, a bursting head breaks apart the old pipe while a new pipe is pulled into the same path. NASSCO says it works best with consistent pipe material, a fairly straight run, consistent depth and enough separation from other utilities. For small sewer laterals, access pits are still needed at each end and some excavation is generally required.
Whether trenchless is possible depends on the pipe. A badly collapsed or misaligned section may not be a candidate for lining, and a camera inspection is how a plumber finds that out. A plumber will recommend what fits your pipe, access and budget.
Who is responsible, and what to check first
SPU and King County both say the property owner is responsible for the side sewer from the building to the public sewer main. SPU says the utility handles the public main, and that a side sewer shared with a neighbor requires the owners to coordinate repairs. Check with your own city or sewer district, because rules and boundaries differ between utilities.
Permit rules also vary. SPU says Seattle does not require a permit for routine side sewer cleaning, but its page does not cover repairs, and King County tells owners to ask their city. Ask before any repair starts.
Before any digging, including landscaping, call 811 so utilities can be marked, and find your side sewer location first. Seattle's tree guidance says to call at least two days ahead.
Preventing root problems
Prevention starts with the landscape. The City of Seattle advises keeping trees at least 5 feet from sewer, water and gas lines. King County advises planting trees and shrubs with low root-damage potential. EPCOR suggests avoiding poplar, willow, elm, ash and birch near sewer lines, though EPCOR is describing conditions in Alberta, so check which species are a concern locally.
EPCOR also lists physical root barriers, installed deep enough to be effective, as a helpful measure. Keeping the pipe in good condition matters as much as the trees, since roots need an opening. SPU recommends flushing only toilet paper and human waste and keeping cooking oil and grease out of drains.
Act on early signs. EPCOR notes that roots can travel far in drought and winter, so a slow drain today can become a blockage.
When to call Pyper Plumbing
Call a plumber if drains are slow in several places, toilets gurgle, a floor drain backs up, or the same clog keeps returning. Pyper Plumbing handles drain cleaning and sewer line repair, along with emergency plumbing and leak detection, in Snohomish, Skagit, Whatcom and Island counties. A plumber can look at the line, explain what is found and describe the repair options that suit your pipe.
If sewage is coming up into the house, stop using water, keep people and pets away from the affected area, and call right away. That is an emergency, not something to wait out.
Common questions
Can tree roots damage a sewer line that is in good shape?
The sources describe roots entering through existing cracks or joints, and say old clay and concrete pipe is most vulnerable. They do not settle whether roots can break a sound pipe by themselves. A camera inspection shows which situation you have.
Will cutting the roots solve the problem?
Usually only for a while. EPCOR says cutting often causes faster, thicker regrowth, and University of Georgia Extension, quoted by the University of Washington, calls mechanical removal temporary.
Is trenchless repair always possible?
No. NASSCO notes that each method suits certain pipe conditions. For example, pipe bursting works best with consistent material and a fairly straight run. A camera inspection helps decide whether trenchless is an option.
Who pays to fix the sewer line between my house and the street?
In Seattle and King County, the property owner is responsible for the side sewer from the building to the public main. Confirm the boundary with your own city or sewer district.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- Seattle Public Utilities: Taking Care of Your Sewer Pipe
- King County: Maintain your side sewer
- City of Seattle: Trees and utilities
- EPCOR: Root growth in sewers
- University of Washington Botanic Gardens Elisabeth C. Miller Library: Tree roots and sewer lines
- NASSCO: Pipe rehabilitation methods
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
