A leaking joint between drain pipes is one of those problems that tends to get worse the longer you leave it. Depending on where the leak is — above ground, below ground, or inside a wall — the fix can range from a straightforward DIY repair to work that legally requires a licensed drainlayer. Read on to understand your options and stay on the right side of NZ regulations.
Why Drain Pipe Joints Leak
Drain pipe joints fail for several common reasons:
- Age and deterioration — rubber seals and solvent-welded joints degrade over time, especially in older PVC or clay pipe systems.
- Ground movement — NZ's seismic activity and soil settlement can shift pipes, pulling joints apart or cracking them.
- Tree root intrusion — roots seek moisture and can force their way into even small gaps.
- Poor original installation — joints that weren't properly cleaned, primed, or glued at the time of installation.
- Thermal expansion — repeated heating and cooling cycles can stress joints, particularly in above-ground waste pipes.
Before reaching for a repair product, it's worth identifying exactly where the leak is and what type of pipe you're dealing with (PVC, cast iron, clay, or copper).
What You Can Legally Do Yourself
In New Zealand, drainlaying is restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006. This means that work on below-ground drainage — including buried stormwater and wastewater pipes — must generally be carried out or supervised by a licensed drainlayer. You can check licensing requirements with the Plumbers Gasfitters & Drainlayers Board.
However, homeowners can typically carry out minor repairs to above-ground waste pipes (e.g., under a sink or basin) without a licence, provided the work doesn't involve connecting to or altering the main drainage system. When in doubt, always check with your local council, as requirements can vary.
Above-Ground Pipe Joints (DIY-Friendly)
For leaking joints on visible waste pipes inside your home:
- Turn off the water supply to the fixture and let the pipe drain completely.
- Clean the joint area thoroughly — remove any grease, grime, or old sealant with a rag and appropriate cleaner.
- Identify the joint type:
- Solvent-welded PVC joints — if the joint has failed, the section usually needs to be cut out and replaced using new fittings, PVC primer, and solvent cement. Products like those from Sika or available at Bunnings or Mitre 10 are commonly used.
- Rubber ring (push-fit) joints — the rubber seal may have perished or slipped. You may be able to disassemble the joint, replace the seal, and reassemble.
- Threaded joints — wrap the threads with PTFE tape and reassemble, or apply a suitable thread sealant.
- Test the repair by running water through the pipe and checking for leaks before closing up any access panels.
Temporary Fixes
If you need to slow a leak while waiting for a professional, a pipe repair clamp or waterproof repair tape (available at hardware stores) can provide a short-term solution. These are not permanent fixes and should not be left indefinitely.
Below-Ground Drain Repairs — Call a Licensed Drainlayer
If the leaking joint is on a buried drain, stormwater pipe, or sewer connection, this is restricted work under NZ law. A licensed drainlayer will:
- Locate the exact source of the leak (often using a CCTV drain camera)
- Excavate safely and repair or replace the faulty joint
- Use approved materials and methods that comply with the NZ Building Code (particularly clauses E1 for surface water and G13 for foul water)
- Arrange any required inspections with your local council
Some below-ground repairs may require a building consent, depending on the scope of work. Your drainlayer or local council can advise — always confirm before starting. You can find guidance on consent requirements at MBIE Building Performance.
Choosing the Right Sealant or Repair Product
| Joint Type | Recommended Approach | Notes |
|---|---|---|
| PVC solvent-welded | PVC primer + solvent cement | Follow manufacturer cure times |
| Rubber ring push-fit | Replace rubber seal | Match seal size to pipe diameter |
| Clay pipe (old systems) | Hydraulic cement or professional repair | Often best to replace the section |
| Cast iron | Rubber repair coupling | Fernco-style couplings work well |
| Threaded fittings | PTFE tape or thread sealant | Clean threads before applying |
Always follow the product manufacturer's instructions and ensure materials are suitable for wastewater use. Ardex and Mapei offer waterproofing and repair products that may be relevant for certain applications.
Safety Considerations
- Wastewater pipes carry harmful bacteria — wear gloves and wash hands thoroughly after any drain work.
- If you suspect the leak has been present for some time, check surrounding areas for mould, rot, or structural damage, particularly in timber subfloors.
- Never work in a confined space near a drain without proper ventilation — sewer gases can be dangerous. Refer to WorkSafe NZ for guidance on working safely.
When to Call a Professional
Call a licensed drainlayer if:
- The leaking joint is on a buried or underground drain
- You're unsure where the leak is originating
- There are signs of significant ground subsidence or root intrusion
- The repair involves connecting to or altering the main drainage system
- You've attempted a repair and the leak has returned
A qualified drainlayer will ensure the work meets the NZ Building Code and is done safely and legally. You can find licensed drainlayers in your area right here on tradedirectory.co.nz.