A broken sewer line usually sits beneath something you'd rather not dig up, a paved driveway, garden beds, a boundary fence, or the path along the side of the house. Until recently, excavation was the only real option. Now pipe relining can fix many breaks without surface disturbance, but the decision hinges on the condition of the pipe, the type of damage, and whether the fault needs removing before a liner goes in.
What relining does
Pipe relining inserts a resin-saturated fabric tube into the broken section of pipe. The tube is inflated, pressed against the host pipe, and held in place until the resin cures. You're left with a smooth, jointless lining inside the old pipe, a structural repair that seals cracks, bridges short gaps, and locks out tree roots. Because it's done from an access point above or downstream, the surface above the fault stays intact.
The method works well under driveways, beneath established trees, and in other spots where excavation would mean jackhammering concrete, moving soil, and re-paving once the new pipe is laid.
When relining suits
Relining works when the pipe's still largely in place and the fault is a crack, joint separation, or root intrusion. The host pipe needs to hold its shape well enough for a liner to conform to it. A clean, intact diameter allows the resin tube to sit flush and cure without folds or voids.
It suits earthenware, cast iron, PVC and concrete sewer lines. Common scenarios include a cracked section beneath the driveway where a vehicle crossing has settled, a joint that's lifted and let roots in, or a length of old earthenware that's fractured but not collapsed.
The repair is faster than excavation and leaves no trench to backfill. There's no need to re-pour concrete, re-lay pavers, or replant garden beds. For properties on the Lower North Shore where driveways are narrow and access tight, the reduction in surface disruption often makes the project possible where excavation would mean blocking the street or removing fences.
When it doesn't
Relining won't fix a pipe that's collapsed, severely offset, or filled with soil. If the sewer has bellied so badly that waste pools and won't move, the liner won't correct the fall, it follows the shape that's already there. If a section has dropped or twisted out of line, the camera will show a sharp step or kink that a fabric tube can't bridge.
Heavy root intrusion can block the path before the liner goes in. Roots need cutting and clearing first. If they've crushed the pipe or pushed a joint so far apart that the gap is wide, excavation may be the only way to restore a sound structure.
Foreign objects, broken grates, chunks of concrete, collapsed inspection openings, sometimes lodge in the line. These need removing mechanically, and if the damage is extensive, digging becomes unavoidable.
Relining also depends on access. The resin tube enters through an existing inspection opening or a small access pit. If the sewer runs under a building slab or through a section with no opening within reach, creating access might require the same surface disturbance that relining was meant to avoid.
How the call is made
A camera inspection shows the fault type, location, and the pipe's general shape. The footage tells you whether the walls are intact, whether the diameter is consistent, and whether any obstacle will stop the liner from seating properly.
If the pipe's cracked but holding its line and diameter, relining usually goes ahead. If it's sagging, kinked, or split so wide that sections have moved, excavation becomes the realistic choice. The decision isn't about preference, it's about what the pipe will accept.
Driveways and time
Relining a sewer under a driveway typically takes a day, sometimes less if the fault is short and access is straightforward. Excavation, reinstatement, and curing time for new concrete can stretch across a week or more. For households that can't afford to lose vehicle access or block a shared driveway, the time difference often settles the question.
Cost sits somewhere between a simple dig-and-replace in open ground and a full excavation under hardstand with reinstatement. It's not always cheaper, but it's usually faster and leaves less mess.
What doesn't change
Whether the repair uses a liner or a new length of pipe, the sewer still needs proper fall, clear diameter, and secure joints downstream. If the problem's isolated to one cracked section, relining handles it. If the whole line is sagging or the grade was never right, relining each fault as it appears won't solve the underlying issue. Sometimes a full replacement makes more sense, even when it means digging.
Relining doesn't fix blockages on its own, it seals the structure after the blockage is cleared. It won't add capacity or change the pipe's route. It's a repair method, not a redesign.
Common questions
How long does a resin liner last? Manufacturers estimate fifty years or more in normal sewer conditions. The cured resin is corrosion-proof and root-proof, and it doesn't rely on the host pipe for strength once it's set.
Can you reline a pipe that's already been relined? Yes, if the first liner is still sound and the diameter allows a second layer. Each liner reduces the internal diameter slightly, so there's a practical limit, especially in 100 mm sewer lines.
Does relining need council approval? Most sewer repairs don't need separate approval if they're like-for-like and don't change the discharge point. Compliance with the plumbing code still applies, and the work must be notified in the usual way.
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If you're weighing up options for a cracked sewer beneath the driveway or garden, a camera inspection will show whether relining suits or whether excavation is the practical path. Call STS Plumbing on 9904 3074 or book a visit.