Tree roots get into sewer and septic lines through cracks and loose joints that were already leaking, not by breaking sound pipe. Research reviewed by the US Forest Service reports that roots cause more than half of all sewer blockages. Removing the tree stops new growth but does not clear the line or repair the defect, so plan on doing both.
If a plumber has just handed you camera footage full of white root hair, here is how to decide what to do about the tree, what to do about the pipe, and which order to do them in.
How do tree roots get into a sewer or septic line?
Through an opening that already exists. Roots follow moisture and nutrients, and a cracked or offset pipe leaks both into the surrounding soil. As NC State Extension puts it, roots cannot create cracks in a sewer pipe, they can only exploit existing cracks or gaps, so roots in the pipe mean the pipe was leaking before the roots arrived.
Once a root tip finds the opening, the inside of a sewer line is an ideal growing environment, and the root thickens where it entered and fans out downstream. The review Tree root intrusion in sewer systems by Randrup, McPherson and Costello, published in the Journal of Infrastructure Systems in 2001, reports that roots are responsible for more than half of all sewer blockages and identifies the risk factors: aged pipes with joints, shallow burial, small-diameter pipes and fast-growing tree species. That list describes a lot of Fraser Valley housing stock, where clay and concrete laterals from the 1950s through the 1970s sit under lawns that have since grown 30 metre conifers.
The same review found that the cost of removing roots may be around one-sixth the cost of replacing or renewing pipe damaged by roots, which is the practical argument for camera inspection and maintenance before excavation.
Which trees are the usual suspects?
Any tree close enough to a leaking pipe. The Randrup review singles out fast-growing species as a risk factor, which in this valley points at cottonwoods and poplars, willows, birches and big maples. Cedars, firs and hemlocks turn up too, mostly because they are everywhere here and enormous.
Distance is less protective than people assume. NC State Extension notes that tree roots can extend two to three times the height of the tree, which puts a mature Fraser Valley conifer’s root system well past the property line in any direction. Planting a tree a few feet further from a line does not change much. A sound pipe does.
Two useful rules of thumb:
- The tree is not the variable you can most easily change. The pipe is.
- Species matters less than pipe age. A 70 year old clay lateral with mortar joints will find roots eventually. A properly bedded modern line with sealed joints usually will not.
Will removing the tree fix the pipe?
No, and this is the most common misunderstanding about root intrusion. Taking the tree down stops that tree from sending new roots toward the line, but three things remain true:
- The roots already inside the pipe stay inside the pipe until they are cut out.
- The crack or open joint that admitted them is still open, and will admit soil, groundwater and the neighbour’s roots next.
- Decaying roots can still hold debris and cause blockages while they break down.
So removal is worth doing when the tree is also a hazard, is in the wrong place, or will keep re-invading a line you cannot afford to replace. It is not worth doing as a substitute for fixing the pipe. If the tree does come out, our tree removal page covers how removals near buried services are handled, and grinding the stump is quoted separately on our stump grinding page.
One caution specific to root work: cutting large structural roots to reach a pipe can destabilize a tree you intended to keep. If a trench has to cross the root plate of a big conifer, expect to have that tree reassessed afterward, because root loss on one side is a classic setup for windthrow in the next atmospheric river.
What happens when roots reach a septic field?
The failure mode is different, and more expensive. A septic dispersal field works by letting effluent seep evenly out of perforated pipe into soil. Roots find those perforations attractive by design, and the US Environmental Protection Agency states plainly that tree and shrub roots can ensnarl and damage drainfield pipes, recommending that a septic professional set the safe planting distance for your system and landscape.
BC’s own guidance is the same. HealthLink BC advises not planting large trees or shrubs near an onsite system because roots may affect the dispersal area, notes that systems typically need servicing every two to five years, and points out that under the Sewerage System Regulation the homeowner is responsible for carrying out a maintenance plan using an authorized person. The EPA’s general guidance is inspection at least every three years and pumping every three to five.
The practical consequence: a compromised field is not a plumbing snake job, it is a septic repair, and in BC the work has to run through an authorized person. That is a different trade from ours. Fraser Valley Septic Service, a separate company, handles septic system repairs including root damage to lines and fields. Our part of the job is the tree above it.
Should you remove the tree, or repair the pipe?
Usually the pipe, sometimes both, rarely the tree alone. Use the situation, not the species, to decide.
| Situation | Sensible move |
|---|---|
| Healthy tree, one cracked run of old lateral | Repair or line the pipe, keep the tree |
| Healthy tree, repeated re-blockage after repair | Repair the pipe properly, then reconsider the tree |
| Tree also has defects, lean or decay | Remove the tree and repair the pipe in the same project |
| Roots into a septic dispersal field | Septic repair first, then decide about the tree with the septic contractor |
| Tree is scheduled to be removed anyway | Do the pipe work while the excavator is already on site |
| Tree sits directly over the line you must dig up | Removal is often unavoidable; check permit rules first |
That last row is where Fraser Valley bylaws show up. The Township of Langley’s fee schedule treats a building envelope, driveway or septic field conflict as its own removal category, charging cash-in-lieu of $600 for a tree 20 to 30 cm DBH and $1,200 for a tree over 30 cm. Mission’s tree bylaw exempts cutting needed under a valid building permit for a private sewage disposal system. Both are worth confirming before a machine arrives, and our guide to what a tree permit costs across the Fraser Valley sets out each municipality’s rules.
How do you keep it from happening again?
You cannot make roots uninterested in water. You can make the pipe uninteresting.
- Fix the defect, not just the symptom. Cutting roots out of a cracked line buys a year or two. Replacing or lining the run buys decades.
- Keep a camera record. Footage before and after the work is what makes quotes comparable and proves what was actually done.
- Plant with the buried infrastructure in mind. Grass over a septic field, trees well off to the side, and no large species planted over a known lateral run.
- Stay on the maintenance schedule. Two to five years for septic servicing in BC, and an inspection sooner if drains slow.
- Deal with the stump properly if the tree comes out. Our guide to stump grinding versus stump removal explains when the full root ball has to come out, which is exactly the case near future foundations, driveways and septic fields.
The bottom line
Roots in a line are a pipe problem with a tree attached. The pipe was already open, the roots found it, and clearing roots without repairing the defect just restarts the clock. Removing the tree helps only when the tree is also a hazard, is in the wrong place, or sits directly over the run that has to be dug up.
If the tree above your line needs to come out, or you want an honest read on whether it should, request a free estimate or book a danger tree assessment and we will look at the tree, the trench route and the permit question together.
Frequently Asked Questions
Will removing the tree get the roots out of my pipe?
No. Removing the tree stops new root growth toward the line, but the roots already inside the pipe stay there and still have to be cut out or the pipe repaired. Removal also does not fix the crack or open joint that let the roots in, and that defect is what will admit soil, water and the next tree's roots. Treat the tree and the pipe as two separate jobs.
Does grinding the stump kill the roots in the line?
It stops regrowth for most conifers, which is the useful part. Cedars, firs and hemlocks do not resprout from roots, so once the stem is gone the root system simply decays in place. Some deciduous species, notably cottonwood, poplar and cherry, can send suckers up from surviving roots and need follow-up. Either way, decaying roots inside a pipe do not clear themselves, and the pipe still needs attention.
How close can I plant a tree to a septic field?
Further than most people plant. Health authorities in BC advise against planting large trees or shrubs near an onsite sewage system because roots may affect the dispersal area, and the US Environmental Protection Agency notes that tree and shrub roots can ensnarl and damage drainfield pipes and recommends letting a septic professional set the distance for your specific system and landscape. Grass over the field, trees well off to the side, is the safe pattern.
How do I know whether the roots are in my line or the city's?
A plumber's camera inspection is the only way to know, and it also shows whether the pipe is cracked, offset or collapsed. Where responsibility for the service connection between the house and the city main sits varies by municipality, so confirm with yours before assuming anyone else will pay. Get the footage and keep it, because it is what makes two repair quotes comparable.
Can a tree be saved if its roots are in the line?
Often, yes. If the tree is healthy and the intrusion is limited to one run of old pipe, replacing or lining that pipe usually solves the problem for decades without touching the tree. Cutting major roots to reach a pipe is the part that can destabilize a tree, so ask the excavation contractor to keep the trench off the root plate where possible, and have the tree looked at afterward if large roots had to be severed.
Is a tree over a septic field a permit issue in the Fraser Valley?
It can be, in the direction people do not expect: removing the tree may need a permit. The Township of Langley's fee schedule sets cash-in-lieu of $600 for a 20 to 30 cm tree and $1,200 for a tree over 30 cm DBH where the removal is for a building envelope, driveway or septic field conflict. Mission's tree bylaw exempts cutting needed under a valid building permit for a private sewage disposal system. Check your own municipality before you cut.
Published August 20, 2026 · Last updated August 20, 2026 · Fraser Valley Tree Service