Key facts: Tree roots in the sewer line
- Roots enter sewer pipes through cracks and loose joints, drawn by moisture and nutrients escaping from the pipe [1].
- Older clay laterals, with a joint every few feet, are the most vulnerable to root intrusion [2].
- Atlanta has one of the densest urban tree canopies of any large U.S. city [3].
- Cutting roots restores flow, but they regrow unless the joints are sealed by lining or replacement [4].
How roots get into a pipe
Tree roots grow toward water and nutrients. A sewer lateral is full of both, and wherever it has a small crack or a joint that no longer seals, a little moisture and warm vapour escape into the surrounding soil. Fine feeder roots grow toward that moisture, find the opening and enter the pipe [1].
Inside, conditions are ideal. The root branches into a dense mass of fine strands across the flow. Toilet paper and solids catch on it, grease coats it, and the pipe narrows. Over time, the roots thicken, which can widen the joint, crack the pipe or push sections out of line.
Signs roots are in your line
- Several drains slowing at the same time, especially the lowest ones
- Toilets gurgling when other fixtures drain
- Backups that return every few months after being cleared
- Problems that get worse in late spring, summer or long wet spells
- A large tree between the house and the street, or close to the line's route
- Roots visible on the cutting head when the line is cleared
Which pipes roots get into
| Pipe material | Root risk | Why |
|---|---|---|
| Vitrified clay | High | Many joints; older joints loosen over time [2] |
| Cast iron | Moderate | Fewer joints, but corrosion and cracks let roots in |
| Bituminized fibre | High once failing | Walls and joints deteriorate with age [5] |
| PVC or HDPE plastic | Low | Few, tight joints; risk mainly at poor connections |
| Cured-in-place liner | Low | Continuous pipe with no joints along its length [4] |
Dealing with roots: the usual sequence
- 1
Cut the roots out
A cable machine with a cutting head, followed if needed by a hydro jetter, removes the roots and restores flow.
- 2
Look inside with a camera
A camera run shows how many joints roots are entering, whether the pipe is cracked or offset, and where.
- 3
Decide: maintain or seal
A few small entry points may be managed with periodic cutting. Many entry points, or cracks spreading from them, point to sealing.
- 4
Seal the openings
Lining covers every joint at once if the pipe is round. Broken or deformed pipe is usually replaced.
Why roots keep coming back
Cutting roots is like mowing a lawn: it removes what is above the surface but leaves the plant alive. The opening the root came through is still there, and the cut root, or a new one, grows back through it. Some lines need cutting every year or two; others clog again within months.
Root-control chemicals are sold for sewer lines, but they do not open a blocked pipe and must be used exactly as labelled. Ask the contractor before putting anything in the line.
The lasting answer is to remove the openings. A cured-in-place liner forms a continuous new pipe inside the old one, with no joints for roots to enter [4]. Where the pipe has collapsed or deformed, replacing it with modern plastic pipe does the same job.
Do you need to remove the tree?
Usually not. Once the joints are sealed, the tree has no way into the pipe. Removing a tree does not seal the openings, and the roots left in the ground keep growing for some time. Large trees also provide shade and value, and in Atlanta, removing or damaging significant trees can involve the city's tree protection rules.
When a repair does involve digging near a tree, ask the contractor to place access pits away from the trunk and limit root cutting. Trenchless methods are often the gentlest option.
Roots and Atlanta's older neighborhoods
Root intrusion is the defining sewer problem in many of Atlanta's older neighborhoods, from Virginia-Highland and Inman Park to Kirkwood and West End. Houses there were built in the clay-pipe era, and many of their laterals have never been replaced. The city's canopy, among the densest in the country [3], has had a century to find every joint.
On compact intown lots, a single front-yard oak can be responsible for roots at a dozen joints. On larger lots in Buckhead, roots can enter far from the house, from trees that seem unrelated to the pipe.
Planting near a sewer line
If you are planting new trees, find out where the lateral runs first. A camera inspection with a locator marks the route on the ground; failing that, the line usually runs from the cleanout or the point where plumbing leaves the house toward the street or a rear easement.
Keep large trees well away from that route and choose smaller, less aggressive species near it. Remember that roots spread well beyond the drip line of the canopy, so what looks like a safe distance for a sapling may not be safe for the mature tree.
For an existing line that has already been lined or replaced with plastic pipe, planting near it is less of a risk, but the connections at each end are still worth keeping clear.
FAQ
Tree root questions
How do I know if tree roots are in my sewer line?
Repeated slow drains and backups, worse in the growing season, with a large tree near the line are strong signs. Roots on the cutting head or a camera inspection confirm it.
How often do roots need to be cut?
The interval varies with the tree, the pipe and the number of openings. A camera check after each cutting shows how fast they return.
Can roots break a sewer pipe?
Roots enter through existing gaps, but as they thicken they can widen joints, crack pipe and push sections out of line.
Will lining the pipe stop roots?
A continuous liner removes the joints roots use. The ends and reconnected branch lines should be checked, since those are the remaining weak points.
Can a neighbour's tree get into my sewer line?
Yes. Roots spread well beyond the canopy, so a tree on the next lot or in the street can reach your lateral.
How far from a sewer line should I plant a tree?
As far as practical, and further for large species, because roots spread well beyond the canopy. Find the line's route first, and choose smaller trees near it.
