How relining works
The old pipe has to be properly clean first, so the drainlayer cuts out roots and jets away scale and fat. A flexible tube soaked in resin is then drawn or turned inside out into the pipe, inflated hard against the old walls and left to set.
Once cured, the lined length is a jointless pipe sitting within the original. Branch connections are cut open again from the inside with a remote cutter, and a final camera run records the finished line.
When relining may suit
- Roots keep returning at the same joints.
- Footage shows cracks or open joints, yet the pipe hasn't collapsed.
- The damage lies under a driveway, slab, deck or a tree you'd like to keep.
- Faults are spread along the run rather than at one point.
Relining or digging
| Relining | Digging and replacing | |
|---|---|---|
| Way in | Existing access points, or a small pit | A trench over the damaged length |
| Best for | Cracked or leaking joints where the pipe is still round | Crushed, collapsed or badly sagging pipe |
| Before work starts | A clean pipe and camera footage | Other underground services located |
| When it's done | Footage of the lined pipe | Ground, paving or garden put back |
When relining isn't the answer
If the pipe has collapsed, or dropped far enough to hold water, there's nothing sound to line, and that section has to be dug up. Some jobs mix the two: a short excavation where the pipe failed, and relining either side.
Relining also can't change where a pipe runs or how steep it is. If the drain needs a new route or more fall, it has to be relaid. Our sewer and drain repairs page covers the digging side.
What changes the job
- Length and diameter of the damaged run.
- How many branch connections need reopening.
- Bends, which make lining harder.
- How much cleaning is needed before the liner goes in.
- Access at both ends of the run.
Is the damaged pipe yours?
Before relining near the boundary, find out who owns that length, because it varies by provider.
Christchurch: the owner maintains a gravity lateral on private land that serves one property. Where a council main crosses private land, the council usually also covers roughly the first metre of the lateral.
Auckland: Watercare says manholes on private land are still its responsibility.
Tauranga: the city council says damage inside the property boundary is the owner's to fix.
Check others in who fixes a blocked drain, and see Christchurch, Auckland or Tauranga for those rules in context.
Before the drainlayer arrives
You can
- Dig out any drainage plans for the property.
- Note the trees and paving over the drain.
- Clear access to inspection openings and the gully trap.
- Collect any earlier camera footage.
Leave to an authorised tradie
- Camera work, and the call between relining and digging.
- Root cutting and cleaning.
- Installing the liner and reopening branches: renewing a drain is drainlaying.
- Any consent paperwork and sign-off.
Licences and consent
Repairing or renewing a drain is drainlaying under the Plumbers, Gasfitters, and Drainlayers Act 2006, so whoever installs the liner needs PGDB authorisation for drainlaying. Owning relining gear isn't the same thing; look the person up on the PGDB register by name, as our licence guide explains.
Schedule 1 of the Building Act exempts repairing drainage with comparable products, and replacing it with a comparable product in the same position, when an authorised person does the work and it meets the Building Code. Whether a particular liner counts as a comparable product is a fair question for the drainlayer, and for the council if there's doubt.
Questions to ask the relining drainlayer
- Can I see the footage before and after lining?
- Which lengths will you line, and will any need digging?
- How will you reopen the branch connections?
- Does this need a consent, and what paperwork will I get?
- What does your written warranty cover?
What we would do
Relining is a good repair in the right pipe and the wrong one in a collapsed pipe, so let the footage decide. Have the drainlayer talk you through each fault on screen, confirm the damaged length is yours before you pay to line it, and favour a drainlayer who digs as well as relines, so the advice isn't shaped by the one tool they own.