AS/NZS 3500 Explained — What Every QLD Plumber Needs to Know in 2026
What Is AS/NZS 3500?
AS/NZS 3500 is the national plumbing and drainage standard that governs how plumbing systems must be designed, installed, and maintained across Australia and New Zealand. It's referenced in the National Construction Code (NCC), the Plumbing Code of Australia (PCA), and QLD's plumbing legislation. If you hold a QBCC plumbing licence, compliance with AS/NZS 3500 is mandatory — not optional.
The 5 Parts of AS/NZS 3500
| Part | Title | What It Covers | Common Jobs |
|---|---|---|---|
| Part 1 | Water Services | Cold and heated water supply, pipe sizing, backflow prevention, materials, pressure | New builds, hot water installs, backflow devices, mains connections |
| Part 2 | Sanitary Plumbing & Drainage | Drainage grades, trap seals, venting, pipe sizing, fixture connections | Bathroom renos, sewer connections, drainage repairs, new builds |
| Part 3 | Stormwater Drainage | Roof drainage, gutters, downpipes, stormwater disposal, charged systems | New roofs, stormwater connections, detention systems |
| Part 4 | Heated Water Services | Tempering valves, solar hot water, heat pumps, expansion control, delivery temperatures | HWS replacements, solar installs, TMV maintenance |
| Part 5 | Housing Installations | Simplified requirements for Class 1 & 10 buildings (houses, sheds) | Residential new builds, granny flats, sheds with plumbing |
Key Clauses Every QLD Plumber Should Know
Drainage Grades (Part 2)
| Pipe Diameter | Minimum Grade | Maximum Grade |
|---|---|---|
| DN 65 | 1 in 40 (2.5%) | 1 in 10 |
| DN 80 | 1 in 60 (1.65%) | 1 in 10 |
| DN 100 | 1 in 60 (1.65%) | 1 in 10 |
| DN 150 | 1 in 60 (1.65%) | 1 in 10 |
Hot Water Delivery Temperatures (Part 4)
| Location | Max Delivery Temp | Requirement |
|---|---|---|
| Personal hygiene (bathrooms) | 50°C | Tempering valve required |
| Kitchen | No limit (typically 60-70°C) | No TMV required |
| Laundry | No limit | No TMV required |
| Early childhood centres, nursing homes | 45°C | Thermostatic mixing valve (TMV) required |
Backflow Prevention (Part 1)
Every connection to the water supply must have appropriate backflow prevention. The hazard rating determines the device required:
- Low hazard — Single check valve or dual check valve
- Medium hazard — Double check valve assembly (DCVA)
- High hazard — Reduced pressure zone device (RPZD) or air gap
How to Look Up Clauses On Site
Carrying physical standards books on site isn't practical. They're expensive ($200+ per part), heavy, and hard to search. Most plumbers end up Googling and hoping for the best.
TradeDesk's AI Standards Reference lets you ask any AS/NZS 3500 question in plain English and get the exact clause, section number, and a practical explanation — all from your phone. It's included in the Pro plan ($79/month or $790/year).
Try the free standards lookup tool or start your 21-day trial.