This is the question we get the moment a drain failure turns from clear it into fix it properly. Both relining and replacement give you a sound drain at the end. The difference is how you get there, how much of your garden, driveway or slab gets torn up on the way, and what it costs once you count the make-good. There is no single winner, the right answer is whichever suits your specific drain, and that is exactly what a CCTV camera survey is for.
What each method actually is
Pipe relining (cured-in-place pipe, or CIPP)
A flexible liner saturated with epoxy resin is pulled or inverted into the existing damaged drain through an access point, inflated so it presses against the old pipe wall, then cured hard in place. The result is a new jointless pipe formed inside the old one. The branch connections are cut back open with a robotic cutter. No trench, no digging up the main run.
Pipe replacement (dig and replace)
The traditional method. Excavate down to the failed drain, remove the old pipe, lay new PVC with correct fall, backfill and reinstate the surface. It is the right tool when the pipe is too far gone to line, or when digging is genuinely easy and cheap.
Where relining wins
- Drains under hard surfaces. Concrete driveways, paved courtyards, slabs, tiled areas. There is no surface to break up and reinstate, which is often the single biggest cost in a dig-and-replace.
- Drains under established landscaping. Mature gardens, retaining walls, decks. Relining preserves all of it.
- Long runs. The longer the run, the more excavation a replacement needs, and the more relining saves.
- Recurring root blockages at cracked joints. The liner is jointless, so there are no joints for roots to enter. That is the permanent end to the every-few-months blockage cycle covered in why your drain keeps blocking.
- Disruption you cannot tolerate. Businesses that need to keep trading, tenants in place, holiday lets between bookings. Relining is usually a day on site, not a week of trenching.
Where replacement wins
- Short isolated failures in open ground. A single broken section under a lawn that is easy to dig is often cheaper to simply cut out and replace.
- Collapsed or badly misaligned pipe. Relining needs a roughly continuous host pipe to form the liner against. If a section has fully collapsed, dropped out of alignment or lost its shape, there is nothing for the liner to follow and you have to dig.
- Severe sag (belly) in the line. Relining follows the existing pipe, so it does not fix a low spot where waste pools. If the problem is incorrect fall, you usually have to excavate and re-lay to correct it.
- Wrong size or wrong layout from the start. If the original drain is undersized or badly designed, replacement lets you fix the design, not just the pipe.
The cost comparison, honestly
People assume digging is the cheap option because the materials are cheaper. PVC pipe is indeed cheaper than a resin liner. But the trench is where the money goes, and the reinstatement after it. As rough Gold Coast guides, relining runs roughly $400-600+ per metre installed, with most residential jobs in the low-to-mid thousands. Replacement is highly variable, a short easy dig in soft lawn can be similar to or cheaper than relining, but the moment the drain runs under a driveway, a slab or established gardens, the excavation plus the make-good (new concrete, re-laid pavers, re-turfing) can equal or exceed the pipe work itself.
The honest rule of thumb: in soft, open, accessible ground for a short failure, replacement is often cheaper. Under any hard or valuable surface, or for any long run, relining usually wins on total cost once you count putting the surface back. We break the relining numbers down further in how much pipe relining costs.
Lifespan and durability
Both methods give you a long-life drain. New PVC laid correctly lasts many decades. A cured-in-place liner has a design life in the order of 50 years and, being jointless, removes the joint cracks that roots exploit. Neither is a compromise on longevity, so durability is rarely the deciding factor, it comes down to access, disruption and total cost.
The tools that decide it: jetter, eel and camera
Before either fix, the drain has to be cleaned and assessed. A high-pressure water jetter scours roots, grease and scale off the pipe wall, an electric eel (drain machine) chews through a blockage on a rotating cable, and a robotic cutter opens junctions and trims roots at branch connections. Then the CCTV camera, paired with a sonde locator that marks the exact position and depth above ground, shows the true condition. That footage is what separates a relining candidate from a must-dig job. You cannot make this call sensibly without it, which is why we camera every drain before quoting a structural fix. The method is explained in how a CCTV drain camera inspection works.
A quick way to think about it
- Cracked joints, root intrusion, intact pipe shape, hard surface above: relining, almost every time.
- Short break, soft open ground, easy dig: replacement is often the cheaper, simpler call.
- Collapsed, dropped, sagging or badly misaligned pipe: replacement, because there is nothing sound to line against.
- Not sure: camera survey first. Always.
What we recommend
We are not wedded to either method, we own the gear for both, so our advice is not steered by what we happen to sell. We run the camera, show you the footage, and quote the option (or sometimes a mix, relining the main run and digging one collapsed section) that fixes your drain for the least total cost and disruption. If a plumber pushes one method without putting a camera down first, be cautious, the decision genuinely cannot be made without seeing inside the pipe.
For the full background, read the pipe relining guide and the blocked drains pillar, or see our blocked drains service. When you want a straight assessment of your own drain, get in touch and we will camera it and lay both options on the table.