Plumber on a residential job: scope, licensing, tolerances, working with other trades

TL;DR

The plumber covers three systems on a residential build (water supply, sanitary drainage, stormwater), with heated water and gas as licensed sub-trades on top. AS/NZS 3500:2025 (four-part Plumbing and Drainage suite, mandatory since 20 October 2025) and AS/NZS 5601.1:2022 (Gas installations) are the binding standards; a Certificate of Compliance must be issued at completion in every state. Plumbing, draining or gasfitting work needs a licence regardless of dollar value in NSW and for gas everywhere, with $22,000 individual / $110,000 company penalties for unlicensed work. Metro hourly rates run $90 to $200/hr ex-GST in 2026; new builds price as a lump sum off the hydraulic plans. Top job-killer is the rough-in landing late or wrong: slab pour, frame inspection and waterproofing all wait on it. In Sydney Water areas, engaging a Water Servicing Coordinator before DA lodgement is the cheapest insurance you’ll buy on Section 73.

What this trade covers

On a residential job the plumber is usually three licensed roles in one body: plumber (water), drainer (sanitary and stormwater), and gasfitter (gas). Most hold all three endorsements, but the licences are separately granted, separately enforced, and separately certified at completion.

On a Class 1a build the scope runs from the water meter and sewer / stormwater connection out to every tap, fixture, HWU, gas appliance, and roof drainage outlet, plus the testing and certification that signs the installation off as compliant. State licensing and CoC forms are in the table below.

What’s in scope (typical residential)

Water supply rough-in (meter to fixtures, cold and hot, pressure tested)
Sanitary drainage rough-in: DWV to boundary trap or sewer
Stormwater rough-in: roof drainage, downpipes, surface drains, discharge connection
Heated water service: install, commission, certify the HWU (gas, electric, heat-pump, solar)
Tempering valve at the HWU per NCC Vol 3 Part B2 and AS/NZS 3500.4 (50°C max at personal-hygiene fixtures: basins, baths, showers; kitchen sinks and laundry troughs excluded)
Gas: consumer piping from meter or LPG bottles to appliances per AS/NZS 5601.1
Wet-area fit-off: tap-ware, mixers, toilet suites, basins, tubs, washing-machine cocks
Final testing per AS/NZS 3500 and the PCA; plumbing CoC (and gas CoC if relevant)
Authority connection where accredited, otherwise via a Water Servicing Coordinator

What’s out of scope (often confused)

Wet-area waterproofing membranes are waterproofer scope under AS 3740. Plumber sets the floor waste; waterproofer membranes around it; tiler beds on top.
Tile bedding and grout is tiler scope. The plumber’s last wet-area act is fixing tap-ware after tiling.
Solar PV and inverter sign-off on a solar-boost HWU is sparky + Clean Energy Council scope.
Refrigeration work in a heat-pump HWU is ARC-licensed; plumber handles only water and pre-wire.
Type B gas appliances (commercial-scale, generally over 10 MJ/hr) need a separate Type B authorisation; residential is almost entirely Type A.
Hydraulic design above a single-dwelling layout is hydraulic engineer scope.
Sydney Water asset works (mains extensions, sewer junction cuts, easements) need a Water Servicing Coordinator.

The quote should state which items are in and which are out. Boundaries between plumber, waterproofer, tiler, hydraulic consultant and WSC are where most variations land.

Engagement basics

Licensing, state-by-state

State	Scheme	Key rule
NSW	NSW Fair Trading licence (individual + contractor); Building Commission NSW administers inspections under the Plumbing and Drainage Act 2011	Any plumbing, draining or gasfitting work requires a licence regardless of cost. Unlicensed penalties up to $22,000 individual / $110,000 company under the Home Building Act 1989. Combined Notice of Work (NoW) and Certificate of Compliance (CoC) lodged via the MyInspections Gateway in Sydney, the Illawarra, Blue Mountains, Newcastle and Hunter.
VIC	Building and Plumbing Commission (formerly VBA): plumbing Registration (supervisor) plus Licence (work for profit), main and specialised classes	A licensee can only do work for profit in a class they hold (or work for someone who does). Compliance Certificate lodged at completion; CC is the consumer’s warranty trigger.
QLD	QBCC: occupational plumber, drainer, or combined	Gasfitting is not QBCC-issued; authorisation comes from the Chief Gas Examiner via Resources Safety and Health Queensland under the Petroleum and Gas (Production and Safety) Act 2004. Form 4 / Form 9 lodged for regulated plumbing and gas work.
WA	Building and Energy (DMIRS), Plumbers Licensing Board: five classes, Provisional Tradesperson to Plumbing Contractor	Most licences run 3-year terms (Provisional 1 year). Gas requires a separate Gas Fitting Permit under the Gas Standards Act 1972. Notice of Intention and Notice of Completion lodged with Building and Energy.
SA, TAS, NT, ACT	CBS / CBOS / NT Government Licensing / Access Canberra Construction Occupations	Verify current licence, insurance and CoC form with the regulator before quoting interstate.

Penalties for unlicensed plumbing or gas work are high in every state and prosecutions are public.

Insurance the plumber should carry

Public Liability: typical floor $5m sole-trader residential, $10m under a head contractor. Statutory PL insurance is a contractor-licence prerequisite in every state.
Workers Compensation: required if any employees or apprentices.
Professional Indemnity: required for hydraulic consultants and designers; many residential plumbers carry it where scope includes design (system layouts, hot-water sizing, gas load calcs).

Current Certificates of Currency should be sighted before work starts. The plumber holds them; the engaging party (usually the builder, sometimes the client direct) confirms them.

Pricing basis

Hourly rate: typical $90 to $200/hr ex-GST in metro AU as of 2026; Sydney averages around $140/hr for standard residential. Used for service work and retrofit.
Call-out fee: typical $60 to $250 on top of hourly, sometimes inclusive of the first hour.
Lump sum off plans: standard for new builds; covers rough-in, fit-off, HWU, gas, testing, and CoCs per system.
PS items for client-pick fittings (tap-ware, mixers, toilet suites, HWU brand). State quantity and per-item rate so variation maths is clean.
Authority charges (Section 73, council stormwater, backflow device registration) usually carried as separate disbursements at cost plus margin.

Hourly work needs a written hours record; lump-sum jobs need a clear scope and a clear hydraulic plan.

Tolerances and acceptance

Plumbing work is judged at PCI against four sources: the contract spec, AS/NZS 3500:2025, AS/NZS 5601.1:2022 (gas), and the HIA Guide to Materials and Workmanship plus the relevant state Guide to Standards and Tolerances (workmanship layer: tap-ware alignment, escutcheon flatness, drain-grate levels).

Compliance, AS/NZS 3500:2025

Non-negotiable, sets the system baseline:

Water (Part 1): pressure-test cold and hot pipework before concealment; backflow prevention sized to hazard rating; non-drinking water fully separated and labelled.
Sanitary (Part 2): minimum drain falls per the current Part 2 tables; all fixtures vented; no unvented S-traps; hydrostatic test at completion.
Stormwater (Part 3): roof drainage sized to design rainfall intensity (Annual Exceedance Probability per current BoM data); legal point of discharge; surface and subsoil drainage where ground conditions require.
Heated water (Part 4): relief valves, expansion control, electrical isolation per the unit’s instructions, plus a tempering valve set to deliver max 50°C at personal-hygiene fixtures per NCC Vol 3 Part B2. TMV field testing, maintenance and replacement follows AS 4032.3:2018.

Compliance, AS/NZS 5601.1:2022

Consumer piping sized to appliance load, leak-tested before commissioning. The headline change in the 2022 edition is multi-layer pipe (PEX-AL-PEX and similar) in new buildings now requires automatic fire isolation (a shut-off valve interlocked to a fire safety system, or for Class 1a an excess flow device or Under Pressure Shut-Off device). Appliances commissioned per manufacturer’s instructions, gas CoC issued, installation registered with the supply authority where required.

Workmanship tolerances (HIA pending)

Numerical limits for plumber-installed fittings are set by the HIA Guide and the relevant state Guide. Values are pending HIA member access.

Item	Guide coverage
Tap and mixer height consistency within a wet area	Per current HIA Guide and state Guide. Pending HIA member access. [HIA-019]
Wall-plate / escutcheon flatness against tile or lining	Per HIA Guide and state Guide. Pending. [HIA-020]
Floor waste / drain grate level and fall consistency	Per HIA Guide and state Guide. Pending. [HIA-021]
Toilet pan, vanity and tub plumb / level	Per HIA Guide and state Guide. Pending. [HIA-022]

Common defects to look for

What inspectors and clients flag at PCI:

CoC missing or in the wrong state form; the OC may be held. Gas CoC is separate from water CoC and the OC needs both.
Drains running back because falls were tweaked during slab pour and never re-checked.
Floor waste set high: water pools instead of running to the grate, only spotted when the wet area is flooded.
Tempering valve missing or set wrong; >50°C at a basin, bath or shower is a defect under NCC Vol 3 Part B2 and AS/NZS 3500.4.
Backflow prevention missing on irrigation, fire systems, or rainwater-tank-to-mains tie-ins.
Tap-ware and escutcheons inconsistent: heights varying within a room, plates not flush to tile or lining.
Roof drainage undersized or unauthorised discharge point; Section 73 not lodged in time, holding subdivision sign-off and OC.

Most rough-in defects are caught with a pre-pour and pre-cover walk; CoC and Section 73 issues surface at OC stage when there’s no time left to fix them.

Subbie quote pack, what should be in it

A complete plumber quote pack covers:

Scope split: water and sanitary rough-in, stormwater, HWU (which, where), gas (which appliances), fit-off per area, testing and CoC per system
Hydraulic plans: drawing numbers and revisions the quote was priced from
Pricing basis: lump sum, hourly, or mixed; variation rate stated; PS items for client-pick fittings
Materials split: HWU and tap-ware often client-supplied; copper, PEX, fittings, valves typically plumber
Programme: days for rough-in vs fit-off; sequencing (slab pour after rough-in tested; tiling before fit-off)
Authority charges: Section 73, council stormwater, backflow registration, supply authority cut-in
Licence and insurance: contractor licence number(s), Certificates of Currency for PL and Workers Comp
Compliance commitment: plumbing and gas CoCs lodged through the relevant portal (MyInspections Gateway in NSW, etc.)
Variation mechanism: pricing, written authorisation, hourly rate for unscoped work

The same list reads from different sides: the engaging party uses it as the quote template; the plumber provides all of it unprompted; the client uses it as the bar the builder should be applying.

Health & safety

Confined spaces: undercrofts, sumps, sewer pits, tank entries. Atmospheric testing, permit-to-enter.
Asbestos: pre-1990 properties may have AC pipe in DWV and meter-cupboard backing. Hazmat survey before disturbing.
Hot work: soldered copper, oxy-acetylene on cast-iron. Hot-work permit, fire watch, extinguisher.
Silica: cutting concrete for floor wastes, core-drilling slabs. On-tool extraction or wet cutting plus P2 RPE.
Manual handling: cast-iron stacks, HWUs, large concrete pits. Two-person lifts default.
Working at heights: roof penetrations, downpipes, vent terminations.
Live gas: leak-test and commission per AS/NZS 5601.1 before reconnect. Smell of gas onsite is a stop-work.

References

AS/NZS 3500.1:2025 Plumbing and drainage, Part 1: Water services (Standards Australia, mandatory from 20 October 2025) (verified 2026-05-05)
AS/NZS 3500 series 2025 update overview (Standards Australia) (verified 2026-05-05)
AS/NZS 5601.1:2022 Gas installations, Part 1: General installations (Standards Australia, current with Amendment 2:2024) (verified 2026-05-05)
NCC 2022 Volume Three, Plumbing Code of Australia (ABCB, Amendment 2 effective 29 July 2025) (verified 2026-05-05)
NSW Government: Plumbing, draining and gasfitting work (verified 2026-05-05)
NSW Government: Combined Notice of Work and Certificate of Compliance (verified 2026-05-05)
Sydney Water: Section 73 Compliance Certificates (verified 2026-05-05)
Building and Plumbing Commission (VIC): Plumbing registration and licensing (verified 2026-05-05)
QBCC: Plumbing and drainage licences (verified 2026-05-05)
WA Building and Energy: Plumbers licensing (verified 2026-05-05)
HIA Guide to Materials and Workmanship, pending member access for numerical workmanship tolerances