Pipe relining vs pipe replacement: an honest comparison
When relining beats digging, when it does not, and what each costs across Sydney. A plain comparison for North Shore homes on old clay sewer lines.
Pipe relining is usually the better choice when the old pipe is cracked or root-damaged but still holds its shape, and when digging would mean breaking up a driveway, sandstone or a protected tree’s roots. Replacement wins when the pipe has collapsed, sags and holds water, is too small, or the ground is already open. A camera inspection decides it.
Key takeaways
- Relining forms a new jointless pipe inside the old one, and suits pipes that are cracked or letting roots in but still hold their shape.
- Replacement is the better fix for a collapsed section, a sag that holds water, an undersized pipe, or ground that is already open for other work.
- On established blocks the pipe is rarely the expensive part. Excavating to it and restoring whatever sits above it usually is.
- Ku-ring-gai Council requires consent for trenching in a protected tree’s root zone or cutting roots 50mm or thicker, unless an exemption applies.
- Footage from a camera inspection of the cleaned line should decide the method, section by section, not the severity of the last blockage.
Jump to a section9
- What pipe relining and pipe replacement actually involve
- Pipe relining vs pipe replacement compared side by side
- When pipe relining is the better choice for North Shore homes
- When replacing a sewer pipe is better than relining it
- How North Shore tree rules affect relining vs replacement
- What pipe relining and replacement cost across Sydney
- How to decide between pipe relining and replacement
- Who pays when a sewer fault is at the Sydney Water junction
- Frequently asked questions
What pipe relining and pipe replacement actually involve
Both jobs end with a sewer line that works. They get there in completely different ways, and the difference decides the cost, the mess and how long your yard looks like a building site.
Pipe relining: a new pipe formed inside the old one
A resin-soaked liner is fed into the damaged pipe through an existing access point, such as an inspection opening or boundary trap, then pressed against the old pipe wall and cured in place. Once it hardens it forms a continuous pipe inside the original, with no joints along its length. The old pipe stays in the ground and acts as the host.
- No trench along the line. Most jobs are done through existing access points, though some layouts need a small access excavation at one end.
- Hours, not days, for the liner to cure on a typical residential run once the line is clean.
- Branch connections are cut back open from inside the liner after it cures, so the fixtures feeding into the line keep draining.
Pipe replacement: dig it up and lay a new line
Replacement is the traditional method. The line is exposed along the length being replaced, the old pipe comes out, and a new PVC pipe is laid on a bed at the correct grade with solvent-welded joints before the trench is backfilled.
Then whatever was sitting on top has to go back: lawn, garden beds, paving, concrete, retaining walls. That last step is the one people underestimate. On most established blocks the pipe work is not the expensive part. Getting to the pipe, and restoring everything above it afterwards, is.
Pipe relining vs pipe replacement compared side by side
This is the comparison most people are actually after. Treat it as a general guide, because the camera footage from your own line overrides any of it.
| What matters | Pipe relining | Pipe replacement |
|---|---|---|
| Excavation | Little or none, through existing access points | A trench along the full length being replaced |
| Surfaces above the pipe | Usually left untouched | Removed, then reinstated at extra cost |
| Time on site | Typically hours for a residential run | Often days, longer through concrete or rock |
| Joints afterwards | None along the lined length | New solvent-welded PVC joints |
| Fixes a sag or dip | No, the liner follows the old pipe | Yes, the new pipe is laid to grade |
| Fixes a collapsed section | No, that section has to be dug out | Yes |
| Internal diameter | Slightly reduced by the liner wall | Full size, or larger if upsized |
| Design life | Liners engineered to a 50-year design life | A new pipe laid to current standards |
| Typical Sydney cost | $450 to $800 per metre for 100mm or $550 to $1,000 for 150mm, plus $2,000 to $4,000 setup | Driven mostly by excavation and reinstatement |
The pattern is simple enough. Relining wins on disruption and on everything sitting above the pipe. Replacement wins wherever the problem is the shape of the pipe rather than its walls.
When pipe relining is the better choice for North Shore homes
Relining earns its place when the pipe is damaged but still round and still running at a sensible fall. That describes a large share of the sewer lines under established North Shore blocks, most of which are earthenware laid before the 1970s: short clay lengths joined roughly every metre, with joints that crack and shift as the ground moves.
It is usually the right call when the camera shows:
- Cracked or open joints along the run, the classic defect in old clay pipe.
- Tree roots coming in at the joints, once they have been cut out. A jointless liner removes the gap they were using.
- Hairline cracks and minor displacement that let water out and roots in without changing the pipe’s shape.
It becomes the clear favourite when the line runs under something expensive or hard to replace:
- Concrete driveways and paved courtyards. Reinstating a concrete driveway alone typically adds $100 to $200 per square metre on top of the pipe work.
- Sandstone. Old sandstone walls, steps and garden edging are part of the character of many North Shore streets, and once pulled apart they rarely go back looking the same. Where the pipe runs through a sandstone shelf, digging slows to a crawl.
- Mature trees. More on this below, because on the North Shore it is often the deciding factor.
- Strata common property. A sewer line under a basement car park or a shared driveway is far easier to line than to dig, and far fewer residents are disrupted while the work happens.
If that sounds like your property, pipe relining across the North Shore is worth pricing before anyone quotes you for a trench.
When replacing a sewer pipe is better than relining it
Relining is not a universal fix, and anyone who says it is has something to sell. A liner takes the shape of whatever it is inside. If the problem is the shape itself, lining it simply preserves the problem in a newer material.
Replacement, at least for part of the line, is usually the honest answer when:
- The pipe has collapsed. A liner needs a host pipe to hold it open. Where a section has caved in, that section has to be excavated and rebuilt, although the rest of the run can often still be lined.
- The line sags or has a belly. A dip that holds standing water will still hold it after lining, and waste settling in that low point keeps causing blockages. Only relaying the pipe at the right grade fixes it.
- The pipe is too small or in the wrong place. Relining slightly reduces the internal diameter. If the line was undersized to begin with, or a renovation needs it moved, a new pipe is the better investment.
- The ground is already open. If you are building an extension, pouring a new driveway or relandscaping anyway, the most expensive part of replacement is already being paid for. Laying a new pipe in an open trench is often cheaper than lining the old one.
- The damage is too severe to line. Large missing sections, lengths that have slipped well out of line, or a badly deformed profile can stop a liner seating properly.
Often the right answer is a combination: dig out one collapsed or sagging section, then line the rest. Where the fault is structural rather than just cracked joints, the call belongs with a plumber who does sewer repairs on the North Shore both ways, so the recommendation is not shaped by whichever equipment happens to be on the truck.
Want this looked at rather than guessed at? Voyager agrees a fixed price before the work starts, and there is no callout fee on eligible jobs.
Call 0485 028 787 or read more about pipe relining on the North Shore.
How North Shore tree rules affect relining vs replacement
Much of the North Shore sits under an established canopy, and councils protect it. That changes the arithmetic of digging in a way most relining guides written for other cities never mention.
Ku-ring-gai Council is the clearest example. Its development control plan counts both of these as injuring a protected tree, which is prohibited without the council’s written consent unless an exemption applies, and both go straight to the heart of a sewer trench:
- Changing ground levels within a tree’s root zone by excavation or trenching.
- Severing roots with a diameter of 50mm or more.
A trench across a garden to replace a sewer line can easily do both. That can mean an application, an arborist’s report and a wait before anyone picks up a shovel, on top of the excavation itself.
The council’s guidance also cuts the other way. Ku-ring-gai’s tree FAQ says its assessment guidelines restrict removing trees that affect sewer and stormwater lines where the pipe can be replaced, relined or relocated. Cutting the tree down is not the default fix. The pipe is expected to be dealt with.
Other North Shore councils have their own tree controls, so check with the council for your address before a trench is planned near a significant tree. Relining, done from inside the existing pipe, sidesteps most of that question.
What pipe relining and replacement cost across Sydney
The relining figures are Voyager’s own rates and the rest are typical across Sydney. All of them are indicative ranges to judge a quote against, not a quote, and they are wide because access, depth and length vary so much from one property to the next.
- Pipe relining: $450 to $800 per metre for a 100mm pipe and $550 to $1,000 for 150mm, plus $2,000 to $4,000 to set up. An 8 metre, 100mm reline comes to $5,600 to $10,400 all up.
- Reopening each branch connection after lining: $300 to $600.
- A CCTV camera inspection before anything is decided: $250 to $550.
- Concrete driveway reinstatement on a dig job: $100 to $200 per square metre, on top of the pipe work.
There is no honest single figure for dig-and-replace, because the pipe itself is rarely what you are paying for. The same ten metres of sewer costs very different amounts under a lawn, under a concrete driveway, or through a sandstone shelf beside a protected tree. That is why relining so often comes out ahead on established blocks, and why it sometimes does not on a bare one. There is a fuller breakdown of what relining costs across Sydney if you want the detail behind those figures.
How to decide between pipe relining and replacement
The decision should come from footage of your pipe, not from how bad the last blockage felt or which method a quote happens to favour.
- Clear the line. A camera cannot see past a blockage, so flow comes first.
- Book a drain camera inspection while the line is clean. Ask for the footage and a marked-up plan showing where each defect sits and how deep.
- Look for the shape problems. A collapse, a sag or a major offset rules those sections out of relining.
- Map what sits above the line. Driveway, paving, sandstone, trees, a pool, a neighbour’s boundary.
- Compare like with like. A relining quote and a dig quote should cover the same length of pipe plus reinstatement, so neither looks cheaper by leaving something out.
| What the camera shows | Usually the better fix |
|---|---|
| Cracked or open joints, pipe still round | Relining |
| Roots entering at the joints | Root cutting, then relining |
| One damaged section, the rest sound | Patch relining |
| A collapsed section | Dig out that section, reline the rest if sound |
| A sag holding water | Relay that length at the correct grade |
| A line too small, or in the way of a renovation | Replacement |
Once you have quotes in hand, the same handful of questions sorts a careful one from a vague one:
- How many metres, and from where to where? A quote that does not name the length and both end points cannot be compared with anything.
- How many branch connections will be reopened, and is that included? On relining this is a common gap between a low quote and a realistic one.
- Is reinstatement included, and to what finish? On a dig job, ask whether the driveway, paving or garden goes back as it was or is left as compacted fill.
- Will I get footage before and after? A camera run after the work is the only proof the liner seated properly and every connection is open.
Who pays when a sewer fault is at the Sydney Water junction
Before comparing quotes, it helps to know which part of the line is yours. Sydney Water owns the junction where your pipe meets its network, but the property owner is responsible for the connection to it, called the point of connection, and for everything on the private side.
- The owner pays to clear tree roots entering the junction, and for damage to it caused by roots or excavation.
- The owner pays for excavating around the junction so it can be fully exposed.
- Where a fault at the point of connection needs excavation deeper than 2.5 metres, Sydney Water may take over the repair.
- If you believe Sydney Water’s junction has failed, do not dig first. It will not reimburse excavation costs unless one of its authorised representatives approved the work.
Relining adds one more thing to ask about. After a liner cures, every live branch connection has to be cut back open. Sydney Water relines its own pipes too, and its guidance for plumbers covers the case where its contractor has left a live junction closed. The same risk exists on a private job, so ask whoever quotes yours how connections are reopened and how that is checked on camera afterwards.
A licensed North Shore plumber can usually tell from the footage which side of the boundary a defect sits on. Voyager Plumbing works under NSW contractor licence 476657C.
Frequently asked questions
Is pipe relining worth it?
Usually, when the pipe is cracked or letting roots in but still holds its shape, and when the line runs under a driveway, paving, sandstone or established trees. It is poor value when the ground is already open for other work, or when the pipe sags or has collapsed, because relining cannot correct either.
How long does pipe relining last?
Modern liners are engineered to a 50-year design life and are designed to outlast the original pipe they sit inside. How long a particular job lasts still depends on the line being properly cleaned and prepared before the liner goes in.
Can a collapsed sewer pipe be relined?
Not through the collapsed section. A liner needs an open host pipe to form inside, so a caved-in length has to be excavated and repaired first. The sound sections either side can often still be relined, which keeps the digging to one spot instead of the whole run.
Does relining make the pipe narrower?
Slightly. The liner has its own wall thickness, so the finished bore is a little smaller than the original. On a correctly sized residential sewer that rarely matters. It matters more if the pipe was undersized to begin with.
Can relining fix a sewer pipe that sags?
No. A liner follows the line of the pipe it is installed in, so a dip that holds water before lining still holds it afterwards. A sagging length needs to be dug up and relaid at the correct grade, although the rest of the line may still suit relining.
Do I need council approval to dig near a tree for a sewer repair?
It depends on the council and the tree. In Ku-ring-gai, trenching within a tree’s root zone and cutting roots 50mm or thicker are among the works that need consent unless an exemption applies. Other North Shore councils have their own tree controls, so check with yours before a trench is planned near a significant tree.
In short
Pipe relining and pipe replacement both fix a failing sewer line, but they suit different faults. Relining is the better choice for cracked or root-damaged pipe that still holds its shape, particularly under driveways, sandstone and protected trees, which covers a lot of North Shore properties. Replacement is the better choice for a collapse, a sag, an undersized pipe or a trench that is already open. A camera inspection of the cleaned line should decide it.
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Mathew is a licensed plumber, drainer and gasfitter, and the owner of Voyager Plumbing. He has held his own NSW contractor licence since December 2016 and is the nominated supervisor on the company licence.
Voyager Plumbing works across Sydney’s North Shore. NSW Contractor Licence 476657C, fully insured, available 24/7.
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