Signs of Tree Roots in Your Sewer

Roots in a sewer line rarely cause a sudden disaster. They send small signals for months first, and learning to read them buys you time.

Plain steps you can follow safely

When to stop and call a plumber

Tools and parts listed up front

Written for Scarborough homes

How roots find the pipe

A mature tree's roots can spread well beyond its canopy, searching for water and nutrients. A cracked joint in a sewer pipe leaks a little warm, moist air and water, and fine roots find it. Inside the pipe they thicken, branch out and catch whatever flows past. Left alone, they can block the line completely or break the pipe apart. Many Scarborough homes built in the 1950s and 1960s have clay or cast iron laterals under lawns shaded by trees planted around the same time, which makes this a familiar local problem.

Reading the warning signs

Go through this checklist and count how many apply to your house.

Look at the yard. Is there a large tree, especially a willow, silver maple or poplar, between the house and the street?
Check the house age. Homes from before about 1970 are more likely to have clay or cast iron laterals.
Watch the toilets. Do they drain slowly or gurgle, even after plunging?
Listen at the floor drain. Gurgling or bubbling when upstairs fixtures drain is a classic sign.
Note the timing. Root problems often get worse in late summer and fall, when trees search hardest for water.
Look for wet spots. A soggy, unusually green patch of lawn over the sewer line can indicate a leak.
Track repeat backups. A drain that clears and then clogs again within months is a strong hint.

Rule of thumb: Three or more ticks on this list is a good reason to book a camera inspection rather than another round of plunging.

Remedies that disappoint

Relying on chemical root killers alone. Some products can slow root growth, but they do not remove a dense mat and they do not repair the crack the roots came through.
Waiting for a full backup. By then, sewage may already be on the basement floor.
Blaming the nearest tree. Roots can travel a long way. Only a camera shows where they actually enter.
Planting new trees over the line. When choosing a spot for a new tree, keep it away from the sewer path.
Ignoring the property line. Part of the lateral belongs to the City. Our older home buying guide explains why this matters when you purchase.

Booking a root cut

If several signs point the same way, a camera inspection is the logical next step. It shows the type of pipe, where roots enter and how much damage there is. From there, a plumber can clear the line with a root-cutting auger and advise whether regular maintenance is enough or whether a damaged section needs repair or lining.

Act quickly if sewage appears in the basement. Stop using water and call. Homes that have suffered a sewer backup should also consider a backwater valve, which protects against City sewer surcharges, though it will not stop a blockage in your own lateral. Read our tree root removal page for how the clearing is done.