How much does drainage work cost in NZ?

Costs vary by scope: a basic drain repair costs $500 to $2,000, a new residential stormwater system costs $5,000 to $15,000, and a full wastewater connection can cost $10,000 to $30,000+. Factors include trench length, depth, ground conditions, pipe material, and council consent fees.

Do I need a building consent for drainage work?

Most drainage work requires a building consent, including new drain installations, alterations to existing drains, and connections to council mains. Minor repairs to existing drains may be exempt under Schedule 1 of the Building Act, but check with your council.

Hiring a Drainlayer Checklist — What to Check Before You Hire | Call A Tradie NZ

Drainage work is underground and out of sight — but when it goes wrong, the consequences are severe: flooding, contamination, and costly repairs. Drainlaying is a regulated trade in NZ, and only PGDB-registered drainlayers can legally install or modify drainage systems. This checklist ensures you hire the right professional.

Registration & Licensing

4 items

Verify PGDB registration on pgdb.co.nz

All drainlayers must be registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB). Search the public register to confirm their registration class and current practising licence.

Check their registration level

Certifying drainlayer — can sign off work and supervise others. Licensed drainlayer — works unsupervised. Registered drainlayer — must work under supervision. For most jobs, you want a certifying or licensed drainlayer.

Confirm their practising licence is current

PGDB practising licences must be renewed annually. The public register shows the status and expiry date. An expired licence means they cannot legally carry out drainage work.

Ask if they hold additional plumbing registration

Many drainage jobs connect to internal plumbing. A drainlayer who is also a registered plumber can handle the full scope, saving you from hiring two separate tradespeople.

Consent & Compliance

5 items

Ask whether your project requires a building consent

Most new drainage installations, alterations to existing drainage, and connections to council infrastructure require a building consent. Your drainlayer should advise on this.

Confirm they will handle council inspections

Council inspectors must approve drainage work before it is backfilled. Your drainlayer should coordinate inspection bookings and ensure work is ready for inspection.

Ask about their as-built documentation process

After completion, as-built drainage plans must be submitted to the council showing the actual pipe locations, gradients, and connections. This is essential for your property records.

Discuss stormwater vs wastewater separation

Many councils require stormwater and wastewater to be on separate systems. Your drainlayer should understand local council requirements and ensure the design complies.

Ask about connections to council mains

Connecting to the council stormwater or wastewater main usually requires council approval and may have specific requirements for pipe size, material, and connection method.

Quotes & Scope

4 items

Get at least three detailed quotes

Drainage quotes should specify pipe material and diameter, trench depth and gradient, connection points, backfill material, surface reinstatement, consent fees, and council inspection costs.

Ask about their approach to site investigation

Before quoting accurately, a drainlayer should investigate existing services, ground conditions, and the location of council mains. CCTV drain inspection may be recommended.

Clarify what is included in surface reinstatement

Drain trenches must be backfilled and the surface restored. Ask whether concrete, asphalt, paving, or lawn reinstatement is included in the quote.

Confirm the warranty on workmanship and materials

Drainage work should carry a workmanship warranty of at least 5 years. Pipe manufacturers typically offer 50+ year warranties on materials. Get everything in writing.

Insurance & Safety

4 items

Request proof of public liability insurance

Drainage work involves excavation near buildings, services, and boundaries. Public liability insurance protects you against accidental damage to your property or your neighbour's.

Ask about their excavation safety practices

Trench collapses are a serious risk. Trenches deeper than 1.5 metres must be benched, battered, or shored. Ask about their trench safety plan and whether they use trench shields.

Confirm they will locate underground services before digging

Power, gas, telecom, and water lines must be located before excavation using beforeUdig.co.nz. Hitting a gas or power line during excavation can be fatal.

Check their environmental management practices

Drainage work can impact stormwater quality and neighbouring properties. A responsible drainlayer manages sediment runoff and ensures no contamination enters waterways.

Red Flags to Watch For

Not registered with the PGDB or has an expired practising licence
Does not discuss building consent requirements
No public liability insurance
Does not locate underground services before digging
Backfills trenches before council inspection
No as-built documentation provided on completion
Uses non-approved pipe materials or fittings
Wants full payment before starting work
No trench safety measures for deep excavations

Drainlayers Hiring FAQ

No. Under the Plumbers, Gasfitters, and Drainlayers Act 2006, only PGDB-registered drainlayers can carry out drainage work. This includes installing, altering, or extending any drain connected to a sewer or stormwater system. DIY drainage work is illegal.