Hiring an excavator to dig a trench on your own section is something most capable homeowners can do — but laying a new water main involves a lot more than just digging a hole. In New Zealand, connecting to the reticulated water supply or installing new water supply pipework is restricted work that must be carried out (or supervised) by a licensed tradesperson. Here's what you need to know before you fire up that digger.
What You Can Legally Do Yourself
As a homeowner, you are generally permitted to:
- Hire and operate an excavator to dig a trench across your own section (no licence is required to operate a small excavator on private land, though safe operation is your responsibility)
- Prepare the trench bed with the correct bedding material (typically fine sand or pea gravel, as specified by your plumber or council)
- Backfill the trench once a licensed plumber has inspected and approved the installed pipework
- Carry out general landscaping and reinstatement after the work is complete
Keep in mind that operating any plant safely is your responsibility. WorkSafe NZ has guidance on safe excavation practices, including shoring requirements for deeper trenches.
What Is Restricted Work — and Why It Matters
Under the Plumbers, Gasfitters, and Drainlayers Act 2006, the installation, alteration, or connection of any water supply pipe (including a new water main from the boundary toby to your home) is restricted plumbing work. This means it must be carried out by, or under the direct supervision of, a licensed plumber registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB).
Doing this work yourself — or having an unlicensed person do it — is illegal and can result in:
- Fines and enforcement action
- Your home insurer declining claims related to water damage
- Difficulties selling your property (LIM reports and building files may flag unlicensed work)
- Serious health risks if the water supply is contaminated or incorrectly connected
Building Consent and Council Approval
Before any spade (or excavator bucket) hits the ground, check with your local council about consent requirements. Installing a new water main connection typically involves:
- A building consent for the new water supply work (though some minor work may be exempt under Schedule 1 of the Building Act — always confirm with your council, as exemptions vary)
- A connection application to your council or water authority to tap into the reticulated supply
- Compliance with NZ Building Code clause G12 (Water Supplies), which sets standards for water supply systems in New Zealand
Your licensed plumber will usually manage these applications on your behalf, but it pays to ask upfront. MBIE Building Performance has useful guidance on when consents are required.
Trench Depth and Pipe Specifications
Getting the trench right matters. Common requirements include:
| Requirement | Typical Standard |
|---|---|
| Minimum cover depth | 450 mm (check with council — can vary) |
| Bedding material | Fine sand or pea gravel, 100 mm below pipe |
| Pipe material | Typically blue-stripe polyethylene (PE) for potable water |
| Marker tape | Blue "Water Main" warning tape laid above the pipe |
| Backfill | Compacted in layers, free of large rocks |
Your licensed plumber will specify the exact requirements based on your council's standards and the NZ Building Code.
Locating Underground Services First
Before you dig anywhere, you must locate all underground services. Striking a buried power cable, gas line, or existing water pipe can be fatal or extremely costly.
- Contact Dial Before You Dig (check their current contact details at dialbeforeyoudig.co.nz or via your council) to get service plans for your area
- Your council may also have as-built drawings showing existing services on your section
- Even with plans, use a cable/pipe locator or proceed carefully by hand near known service routes
WorkSafe NZ treats unplanned contact with underground services as a serious hazard — don't skip this step.
Practical Tips for Using a Hired Excavator
- Choose the right machine: A 1.5–3 tonne mini excavator is usually sufficient for residential trenching. Hire companies at Bunnings or specialist hire yards can advise on bucket width.
- Plan your spoil: You'll generate a significant amount of excavated material — have a plan for where it goes on your section.
- Work with your plumber: Coordinate the dig so your plumber can inspect the trench bed before the pipe goes in, and again before backfilling.
- Protect the trench: If the trench will be open overnight, fence it off for safety, especially if children or animals are present.
When to Call a Professional
You must engage a licensed plumber for all water supply pipework installation and connection. You should also consider hiring a professional earthmover if:
- The trench is deeper than 1.5 metres (shoring may be legally required)
- You're working near existing structures, retaining walls, or tree roots
- The ground conditions are unstable, rocky, or waterlogged
- You're not confident operating an excavator safely
A qualified earthmover and a licensed plumber working together will get the job done safely, correctly, and to code. You can find experienced local tradespeople — including earthmovers and plumbers — right here on tradedirectory.co.nz.
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