Replacing a cracked drain pipe sounds like a straightforward dig-and-swap job, but in New Zealand the law draws a clear line between what you can do yourself and what must be carried out by a licensed drainlayer. The short answer: most drain pipe replacement work is restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006, meaning a licensed professional must do it — and in many cases a building consent is also required. Read on to understand exactly where the boundaries sit and how to get the job sorted safely.
What Counts as Restricted Drainlaying Work?
Under NZ law, drainlaying is a licensed trade regulated by the Plumbers, Gasfitters and Drainlayers Board (PGDB). Restricted drainlaying work includes:
- Laying, altering, repairing, or replacing any drain (the pipe that carries wastewater from your house to the public sewer or septic system)
- Connecting to or disconnecting from a public sewer
- Any work on stormwater drains that form part of the building drainage system
If you carry out restricted drainlaying work without a licence, you could face significant fines, your home insurance may be voided, and — most importantly — a faulty drain can cause serious health and environmental hazards.
What Can a Homeowner Legally Do?
As a homeowner, you are generally permitted to:
- Dig the trench to expose the damaged pipe (the physical excavation itself is not restricted)
- Identify and photograph the cracked section to help your drainlayer quote accurately
- Clear surface-level blockages using a plunger or drain snake on fixtures you own
- Reinstate the ground (backfilling and landscaping) after a licensed drainlayer has signed off on the repaired pipe
However, the actual cutting out and replacing of the pipe, joining new sections, and testing the drain must be done by — or under the direct supervision of — a licensed drainlayer. Always confirm the scope of any work with your drainlayer and your local council before you start.
Do You Need a Building Consent?
This depends on the nature and extent of the work. Under Schedule 1 of the Building Act 2004, some minor drainage repairs may be exempt from building consent — but this is not automatic. Factors that affect whether consent is needed include:
- Whether the work involves a new connection to the public sewer
- The length and depth of pipe being replaced
- Whether the work affects a shared or public drain
Always check with your local council before work begins. Your licensed drainlayer will usually be able to advise you on consent requirements, and MBIE Building Performance has useful guidance on when consents apply.
How to Identify a Cracked Drain Pipe
Common signs of a cracked or broken drain include:
- Slow draining or recurring blockages
- Wet patches or sinkholes in the lawn above the drain line
- Foul smells from the garden or inside the house
- Rodent activity near the drain line
- Lush, unusually green grass over the pipe route (from leaking effluent)
A licensed drainlayer can confirm the damage using a CCTV drain camera inspection before any digging begins — this saves time and money by pinpointing the exact location and extent of the crack.
The Repair Process (What Your Drainlayer Will Do)
Once the damaged section is located, a typical repair involves:
- Excavating the trench to expose the pipe (you may be able to assist with this under supervision)
- Cutting out the cracked section
- Installing new pipe — commonly uPVC in NZ, jointed with solvent cement or rubber-ring push-fit couplings
- Testing the repaired drain (usually a water or air pressure test)
- Backfilling the trench with appropriate bedding material and compacting in layers
- Issuing a Certificate of Compliance (CoC) for the work
The CoC is an important document — keep it with your property records.
Pipe Materials and Costs
Most residential drains in NZ are either uPVC (modern homes) or clay/earthenware (older homes, pre-1970s). Replacement is almost always done with uPVC, which is durable, readily available from suppliers like Placemakers and Mitre 10, and straightforward to join.
As a rough guide only, drain repair costs in NZ can vary enormously depending on depth, length, access, and location. Get at least two or three quotes from licensed drainlayers.
Safety Considerations
- Trench collapse is a real danger — trenches deeper than 1.5 m require shoring or battering under WorkSafe NZ guidelines. Never enter an unshored deep trench.
- Call Before You Dig (0800 248 344 or cabdnz.co.nz) to locate underground services before any excavation.
- Wastewater contains pathogens — wear gloves and wash hands thoroughly if you come into contact with drain contents.
When to Call a Professional
You should engage a licensed drainlayer for any work that involves cutting, joining, or replacing drain pipe. This is not optional — it is a legal requirement under NZ law. A licensed drainlayer will also ensure the work meets the NZ Building Code (in particular clauses G13 – Foul Water and E1 – Surface Water) and will issue the required Certificate of Compliance.
You can find qualified, local drainlayers on tradedirectory.co.nz. Always check that your drainlayer holds a current licence with the PGDB before work begins.