Standard advice when roots crack a sewer line runs roughly: clear it, then deal with the tree. It is the answer you will get from most plumbers, most search results and most neighbours, and in most of Sydney it is a reasonable one.
It does not work here. Hornsby Shire markets itself as the Bushland Shire and means it: Council significantly strengthened tree protection, and all trees are now protected apart from a limited list of species treated as weeds or hazards. So the usual advice starts with a step you may simply not be allowed to take, and the repair has to be designed around a tree that is staying where it is.
In this shire a tree over five metres tall, or with a canopy spread over five metres, needs Council approval to prune or remove. That is a permit process taking around three to four weeks that may be refused, not a same-week decision. So the sensible repair is one that does not depend on the tree going: clear the roots, then reline the pipe so there is no entry point left for them to use.
- Assume the tree is protected until Council says otherwise
- Do not plan a repair that depends on removal being approved
- Clear the line, then get it camera inspected
- Reline to close the entry point without touching the tree
- Council is the authority on every question about the tree itself
On this page
1. What the rule actually says
Council strengthened tree protection so that all trees are protected, with a limited list of exceptions for species considered weeds or hazards. In practice the trigger most homeowners meet is size: a tree over five metres tall, or with a canopy spread greater than five metres, needs Council approval before it is pruned or removed.
Getting that approval means a Tree Preservation Order application to Council. There is a fee, and a processing period measured in weeks rather than days. Both are set by Council and both change, so the figures to rely on are the ones Council publishes, not ones repeated on a plumber's page.
The important word in all of that is "application". It is a request that may be refused, on a timeframe measured in weeks. Anybody planning a drain repair around it is planning around an outcome they do not control.
We can tell you how this changes a repair. We cannot tell you whether your particular tree qualifies for an exemption, and neither can anyone quoting to remove it.
2. Why the exemptions rarely help with a sewer line
There are exemptions, and they are narrow. The one people reach for is the foundation exemption: a tree may be removed without a permit where the base of the trunk is within three metres of the foundation of an approved building.
That exemption is designed for a completely different problem, and it almost never covers the tree causing a drainage issue. A sewer run leaves the house and crosses the yard, so the tree sitting over it is generally well beyond three metres from the building. It is also, on these blocks, generally over five metres tall.
Other exemptions exist where Council accepts a tree is dead or dying and is not fauna habitat, or where it is under three metres tall and not in bushland. And exemptions do not apply at all inside a Heritage Conservation Area or a listed ecological community, which covers real parts of this shire.
The practical summary is that the tree over your sewer is probably protected, and proceeding as though it is not is how people end up in trouble.
3. What roots are actually doing to the pipe
Worth being precise about this, because it is what makes the alternative work.
Roots cannot break into sound pipe. They grow toward moisture, and what attracts them is a defect already releasing it: an opened joint, a hairline crack, an unsealed junction. Fine roots enter through that opening, then thicken inside the pipe where the conditions are ideal.
So the root is not the beginning of the story. The opening is. And that means there is a fix that has nothing to do with the tree at all: close the opening, and the roots have nowhere to go, regardless of how large or healthy the tree above is.
4. The repair that works around a tree that is staying
- Clear the line first. Mechanically cut the roots out to restore flow. This is necessary and it is not the fix.
- Camera it immediately afterwards. The footage shows where the roots were entering, over what length, and what condition the pipe is in.
- Reline the affected section. A new pipe wall formed inside the old one, continuous and without joints, so there is no opening left to re-enter through.
- Keep the footage. It is your evidence about what was done and a baseline for anyone looking at the line in ten years.
That sequence never requires anybody to touch the tree, which on these blocks is the entire point. It also avoids the second permission problem: excavating beside a protected tree risks its root zone, and that is its own approval question rather than a way around the first one.
Roots in the line and a tree you cannot touch?
That is the ordinary situation here. We will clear it, film it and line it.
5. Why the excavation option is worse here than elsewhere
Replacing a damaged section by digging it up is a legitimate repair in general. On a block with a protected tree over the line, it carries a problem that has nothing to do with plumbing.
A trench next to a mature tree cuts through its root zone. Damaging that is capable of harming or killing the tree, which is exactly the outcome the protection exists to prevent, and it can be an approval matter in its own right.
So the homeowner who digs to avoid a permit conversation can end up in a worse permit conversation, having also paid for a trench. Relining sidesteps both, which is why it is not simply the tidier option in this shire but frequently the only sensible one.
6. Living with a protected canopy over your drainage
- Treat a slow drain as early information. On these blocks it is usually the first sign.
- Get the line filmed once so you have a baseline rather than a memory.
- If the same fixture is slow every year, that is a defect, not a season.
- Before any landscaping or building work near a tree, ask Council first. It takes weeks, so it belongs at the start of a project rather than partway through.
- Plant new large trees with the drainage route in mind. It costs nothing at planting and a great deal at every other time.
- Keep any Council correspondence about a tree with the house papers.
None of this is an argument against the trees. They are why a great many people live here. It is an argument for designing the plumbing around them rather than the other way round, because the plumbing is the part you are allowed to change.
- In this shire all trees are protected apart from a limited list of weeds and hazards.
- Over five metres tall, or over five metres of canopy, means Council approval to prune or remove.
- Council's permit process takes weeks rather than days, and it may be refused.
- The foundation exemption almost never covers the tree over a sewer run crossing the yard.
- Roots enter through an existing defect, so closing that defect solves it without the tree.
- Clear, film, then reline. Digging beside a protected tree risks its root zone and its own approval.
Protected trees and drains FAQs
Can I remove a tree that is damaging my sewer?
Only with Council approval, unless a narrow exemption applies. Damage to drainage is something Council will consider as part of an application, but it is an application rather than an automatic right. They are the authority and worth talking to directly.
What if the tree is close to the house?
There is an exemption where the base of the trunk is within three metres of the foundation of an approved building. It rarely helps with a sewer problem, because the run crosses the yard and the tree over it is usually well beyond that distance.
How long does a tree application take?
Council sets both the fee and the timeframe, and the honest answer is that it is measured in weeks rather than days. Check the current figures with Council directly rather than trusting a number on a trade website. The point that matters is that it is neither immediate nor guaranteed.
Will relining stop the roots for good?
It removes the entry point, which is what roots exploit. A continuous liner has no joint for a root to find. Where a line has multiple defects along its length, the question becomes how much of it to line, and the camera footage answers that.
Can you dig instead and just be careful?
Sometimes, but it is worth understanding what you are taking on. A trench beside a mature tree cuts its root zone, damaging a protected tree is its own problem, and you may end up having the permit conversation anyway having already paid for the excavation.
The roots came back a year after clearing. Is that normal?
Yes, if only the roots were cut. Clearing restores flow and leaves the opening. Regrowth into a cleared line is the expected outcome rather than a sign of poor work, which is exactly why the footage and the liner matter.