Diagnosis

Tree Roots in Sewer Lines: Why Minneapolis Has So Many

By Minneapolis Sewer Line Repair · September 9, 2026 · 5 min read

Pull a camera out of a Minneapolis sewer lateral and the odds are good it comes back with roots on it. Tree roots in a sewer line are the single most common thing we find in this city, and it isn't bad luck. It is the combination of what the city planted on its boulevards and what it buried under them.

The pipe: clay with a joint every few feet

Almost every house built here between 1900 and 1955 got a vitrified clay lateral — fired clay pipe in two- and three-foot lengths, each one slipped into the bell of the next and sealed with mortar or a tar compound. A 70-foot lateral has 25 or 30 joints. Clay itself is nearly indestructible underground; the joints are the weak point. A century of frost heaving the ground five feet deep, the house settling on its block foundation and the street loading the soil differently from the lawn has opened most of them at least a little.

A root does not need much. A hairline gap at a joint leaks a little moisture and nutrient-rich vapor into the soil, and a root growing through that soil turns toward it.

The trees: the boulevard program

Minneapolis has one of the most complete boulevard tree canopies in the country, and the boulevard is exactly where the lateral runs on its way to the main. The species matter.

• American elm. The original boulevard tree. Most were lost to Dutch elm disease in the 1970s and 80s, but the stumps and the roots stayed, and the survivors along streets like Nicollet and in Kenwood are enormous. Elm roots are aggressive and shallow.
• Silver maple. Planted everywhere as a fast replacement. Silver maple roots are legendary for finding water — they lift sidewalks and fill sewers.
• Green ash. The second replacement wave, now coming out across the city for emerald ash borer. Cutting the tree does not remove the roots, which keep growing for a season and then rot, leaving channels for the next tree's roots to follow.
• Linden and hackberry. The current planting choices. Better behaved but still trees, still growing roots toward moisture.
• Cottonwood and willow. Rare on boulevards, common in backyards along the creek corridors in Southwest and near the lakes. If one is within 40 feet of the lateral, it is in the lateral.

How a root gets from a hair to a blockage

1. A fine root enters an open joint and finds water and nutrients.
2. It thickens, and the pressure of a growing root pries the joint wider.
3. Side roots branch off inside the pipe and form a mat across the flow.
4. Paper, wipes and grease catch on the mat, and one laundry day the basement floor drain backs up.

By stage three the joint is broken, not just open. Which is why cutting the roots and walking away is a six-month fix.

Why clay, not the tree, is the real problem

People ask whether they should take the tree down. Usually no. A healthy boulevard tree is worth thousands in shade and property value, the city owns the boulevard trees and has rules about removing them, and the roots of a removed tree keep working for a year anyway. The problem is the open joint. Fix the pipe and the roots have nowhere to go.

On a PVC replacement or a cured-in-place liner, the joints are gone. We have never scoped a properly installed liner and found a root inside it.

Fixes that last and fixes that don't

If the camera shows roots at one or two joints and clean pipe elsewhere, a spot repair at $1,500–$4,000 solves it. If roots are at most joints, annual hydro jetting is a reasonable way to manage a line for a few years, and trenchless lining at $6,000–$15,000 is the way to be done with it — without disturbing the tree.

A note on root killers

Copper sulfate and foaming herbicide products kill roots on contact and slow regrowth. They do not close a joint, they can harm the tree if overused, and some products are restricted for sewer use because the copper ends up at the treatment plant. On a sound pipe with light roots they are a fine supplement to jetting. On a broken joint they are a way to spend $40 a year not fixing a $3,000 problem.

The practical rule

Every Minneapolis house with a clay lateral and a boulevard tree should have been scoped at least once. If yours hasn't, that is the first call. Timing matters too: root growth peaks in late summer and backups follow in fall, which is why root season is a thing here.