Reline 09 6 min read Guide
Relining or digging: an honest comparison
When trenchless wins, when excavation is genuinely the right call, and how to price the two fairly once the garden is in the sum.
Short answer: reline when the pipe still holds its shape, dig when it does not. Most cracked and root invaded Sydney sewers can be relined without a trench. The honest comparison prices everything the excavator touches, not just the pipe.
What each method actually does
Excavation replaces the pipe by removing everything above it first. Relining rebuilds the pipe from the inside: the line is jetted clean, a resin saturated liner is inverted through it, cured hard, and proven on camera. One method arrives with a trench. The other arrives through the inspection opening you already have.
Excavate and replace
Cured in place reline
Trench through lawn, paving or driveway.
Access through existing openings. Surface untouched on most jobs.
Days on site, plus reinstatement weeks later.
Most single lines done in a day, back in service that evening.
Cost of the pipe, plus the cost of everything above it.
Setup plus a rate per metre, from a published card.
Right call for collapsed or back graded lines.
Right call for cracked, root invaded, still round lines.
Price the whole job, not the pipe
A dig quote that looks competitive usually stops at the trench. Add the driveway slab it crosses, the turf, the garden bed, the fence panel that comes out for machine access, and the second contractor who does the reinstatement. Then add the week you spend living around an open trench. The reline number on our card is the whole number: survey, clean, liner, junctions, proof pass, warranty.
The excavator reflex
Be wary of any operator who reaches for the dig before the camera. Digging blind is how a
single cracked joint becomes a wrecked yard. Buyer forums are full of five figure
replacement quotes for faults a camera would have shown to be one patch.
The three honest reasons to dig
First, full collapse: if the bore has closed, a liner has nothing to travel through. Second, grade failure: a liner follows the old pipe, so a line laid without fall has to be re laid, not relined. Third, planned works: if a renovation is trenching that ground anyway, replacement can ride along. Everything else, cracks, root entries, displaced joints, open joints, misaligned collars, is reline territory.
How to decide, in order
- Get the CCTV survey and watch the footage. The pipe tells you which method it needs.
- Ask any dig quote to include reinstatement of everything above the trench.
- Ask any reline quote for the per metre split and the post cure proof pass.
The camera settles it
This is not a philosophy debate. The footage shows whether the bore is intact, where the
faults sit and what the fall is doing. Either method quoted without that footage is a guess
with a dollar sign on it.
Common questions
Is relining as strong as a new pipe?
A cured in place structural liner is a new pipe, formed inside the old one. It is not a coating. Design life runs beyond 50 years, which is why the warranty is 50 years in writing. The old pipe becomes formwork; the liner does the work.
When is digging genuinely the right call?
When the line has fully collapsed and lost its bore so a liner cannot pass, when the pipe is badly back graded and needs re laying to fall, or when a renovation is opening the ground anyway. A camera survey identifies all three honestly.
Is relining cheaper than excavation?
On the pipe alone the figures can look similar. Add what excavation destroys, lawn, paving, driveways, garden beds, plus reinstatement and days of disruption, and the reline is usually clearly ahead. Compare whole job to whole job, not trench to liner.