Drainlaying and plumbing are two distinct licensed trades in New Zealand, regulated under the same legislation but with different scopes of work. Some tradespeople hold licences in both areas, which means they can legally carry out work across both trades on the same job — but not all drainlayers are also licensed plumbers, so it's important to check before you hire.
How Licensing Works in NZ
Both plumbers and drainlayers are regulated by the Plumbers, Gasfitters and Drainlayers Board (PGDB), which is the licensing authority under the Plumbers, Gasfitters, and Drainlayers Act 2006. The PGDB issues separate licences for each trade:
- Licensed Drainlayer — authorised to install, alter, or repair drains and sewers from the building to the point of connection with the public network.
- Licensed Plumber — authorised to work on sanitary plumbing inside the building, including pipes, fixtures, and fittings connected to the water supply and drainage system within the structure.
- Licensed Gasfitter — a third separate licence for gas fitting work.
A tradesperson can hold more than one of these licences. Someone who is both a licensed plumber and a licensed drainlayer can legally carry out work across both scopes on the same project — which can be very convenient for homeowners, as it means fewer contractors to coordinate.
What Is Restricted Work?
Both plumbing and drainlaying are classed as restricted work under NZ law. This means it is illegal for an unlicensed person — including a homeowner — to carry out this work themselves. All restricted sanitary plumbing and drainlaying must be done by, or under the direct supervision of, a licensed tradesperson. Once the work is complete, the tradesperson must issue a Certificate of Compliance (CoC), which is your legal record that the work meets the NZ Building Code.
The relevant Building Code clauses for this type of work include:
- G12 — Water supplies
- G13 — Foul water (drainage)
- E1 — Surface water
Where the Two Trades Meet
The boundary between plumbing and drainlaying is roughly the point where internal sanitary pipework exits the building and connects to the underground drain. In practice, this junction is where the two trades overlap, and it's a common source of confusion for homeowners.
| Work Type | Who Can Do It |
|---|---|
| Underground drain to street connection | Licensed Drainlayer |
| Stormwater drainage and soakage | Licensed Drainlayer |
| Internal waste pipes and fixtures | Licensed Plumber |
| Hot and cold water supply pipework | Licensed Plumber |
| Connection point (inside to outside drain) | Licensed in both trades, or two separate contractors |
| Gasfitting | Licensed Gasfitter |
Can One Contractor Do Both?
Yes — if they hold both licences. Many experienced tradespeople in NZ do hold dual licences, particularly those who have worked in the industry for a number of years. When getting quotes, simply ask the contractor to confirm which PGDB licences they hold. You can also verify a tradesperson's licence status directly on the PGDB website using their online register — this is a quick and easy check that's well worth doing.
Hiring a dual-licensed contractor can save time and money on jobs where both trades are needed, such as:
- New bathroom or laundry additions
- Relocating a toilet or shower
- Connecting a new dwelling to the sewer
- Replacing old drainage and internal plumbing at the same time
Building Consents and Your Council
Depending on the scope of work, a building consent may be required before any plumbing or drainlaying begins. Some minor work may fall under Schedule 1 of the Building Act 2004 (exempt from consent), but this varies — always check with your local council before starting. Your tradesperson should be able to advise you on this, but the final call rests with your council.
For more guidance on what requires consent, visit MBIE Building Performance.
Safety Note
Never attempt restricted plumbing or drainlaying work yourself. Incorrect work can result in sewage contamination, water damage, health hazards, and significant legal liability. It can also void your home insurance. Always use a licensed tradesperson and obtain a Certificate of Compliance on completion.
When to Call a Professional
You should contact a licensed plumber, drainlayer, or dual-licensed contractor whenever you need to:
- Repair or replace any underground drain
- Install or move any sanitary fixture (toilet, basin, shower, sink)
- Connect to the public sewer or stormwater network
- Investigate a blocked or broken drain
- Carry out any work that touches the water supply or waste system
If you're unsure who you need, start by describing the full scope of work to a contractor and ask whether they hold the relevant PGDB licences. You can find qualified local drainlayers and plumbers on tradedirectory.co.nz.
Certifying Drainlayer
