Plumbing on a Queensland new build is notifiable work, which means it has to be inspected at defined stages to confirm it meets the standards before it gets covered up or signed off. The inspections are not optional and the build cannot legally progress past certain points without them. The most critical is the pre-slab drainage inspection, because once the slab is poured the under-slab drainage cannot be seen or changed. Below is what gets inspected, who does it, and where it sits in the build. We also cover the staging in our new build plumbing stages guide.
Who carries out the inspections
Plumbing inspections in Queensland are carried out either by a council plumbing inspector or by a licensed plumbing certifier engaged for the build. On the Gold Coast, council inspections go through Gold Coast City Council's plumbing inspectors, and many builds use a private certifier for the broader building approval. The inspector is independent of the plumber doing the work, which is the point, an independent check that the work meets the code. The standard the work is assessed against is AS/NZS 3500, the national plumbing and drainage standard, along with the Queensland Plumbing and Wastewater Code and the Plumbing Code of Australia.
The pre-slab drainage inspection, the critical one
This is the inspection that matters most and the one that cannot be skipped or rushed. Before the slab is poured, the under-slab drainage is laid out, the falls are set, the penetrations are positioned, and the sewer or septic connection is run. The plumbing inspector checks that the drainage is laid to the minimum fall required under AS/NZS 3500, that the layout matches the approved plans, that the pipe materials and jointing are correct, and that the falls will run to the sewer under gravity. The slab pour cannot legally proceed until this inspection passes.
The reason this inspection is so important is that everything it checks gets buried under concrete minutes later. If a drain is laid with insufficient fall and the slab goes on top, the only fix is to cut the slab open. The pre-slab inspection is the safeguard against that. We book it with proper lead time, because a council plumbing inspection typically needs several working days' notice and you cannot book it Friday for Monday. We explain why the pre-slab decisions are locked forever in what plumbing you decide before the slab is poured.
The rough-in stage and pressure testing
After the frame is up, the hot and cold water lines, the above-ground drainage and the gas lines are roughed in through the frame. Before the plasterer closes the walls, the rough-in is pressure-tested to confirm there are no leaks. The hydrostatic pressure test is documented for the compliance pack. Depending on the build and the certifier, the rough-in may be inspected at this stage as well, because once the plasterboard goes on, the pipework in the walls is hidden. The principle is the same as pre-slab, anything that gets covered up gets checked before it is covered.
Sewer and drainage connection inspection
The connection of the house drainage to the council sewer main is inspected to confirm it is done correctly and sealed properly. On a property not connected to mains sewer, the on-site treatment system takes the place of the sewer connection and has its own inspection, covered below. The drainage connection inspection confirms the tie-in to the council infrastructure meets the standard.
Septic or AWTS inspection on unsewered properties
Acreage and rural-residential builds in the Gold Coast hinterland that are not on mains sewer use an on-site treatment system, either a septic system or an aerated wastewater treatment system (AWTS) compliant with AS/NZS 1547. The installation and the disposal field are inspected by the council before the system is commissioned. These inspections often need longer lead time than a standard plumbing inspection, particularly in the busy season, so they have to be booked well ahead. The on-site system inspection is a council requirement and the certifier will not sign the build off without it. We touch on on-site systems in the new build plumbing guide.
Backflow prevention inspection and testing
If the build has any backflow risk, for example an irrigation system, a pool or pond top-up, a rainwater-to-mains connection, or certain outdoor taps, backflow prevention devices are required to protect the drinking water supply. Testable backflow devices have to be inspected and tested at installation, and the testing is documented with a backflow prevention testing certificate. Testable devices then need periodic re-testing through the life of the property, usually annually, but the new-build requirement is the initial installation and test.
Gas inspection and compliance
Gas is separate from the water and drainage plumbing and is handled by a licensed gas fitter. Any gas installation, whether natural gas or LPG, has to be tested and a gas compliance certificate issued by the licensed gas fitter for every gas appliance installed. Gas work is its own licensed discipline with its own compliance paperwork. Most new builds with a gas cooktop, gas hot water or gas heating need both the plumbing compliance and the gas compliance certificates. We provide both, see our gas fitting service for the gas side.
The final inspection and commissioning
At completion, the full system is commissioned and final-tested. A final hydrostatic test is run on the complete system, every fixture is tested, the hot water unit is commissioned, and the gas appliances are leak-tested and certified. The final inspection confirms the finished plumbing complies with AS/NZS 3500 and the relevant codes. Once everything passes, the licensed plumber issues the QBCC Form 4 plumbing compliance certificate.
The QBCC Form 4 ties it all together
The QBCC Form 4 is the plumbing compliance certificate the licensed plumber issues at completion, certifying that the work was done by a licensed plumber, complies with AS/NZS 3500 and the Plumbing Code of Australia, has been pressure-tested, and that drainage falls and any backflow devices are correct. You cannot get your certificate of classification, the document that lets you legally move in, without the Form 4. It is the paperwork outcome of all the inspections through the build. We explain it in full in what is QBCC Form 4 and do I need it.
The compliance pack you should receive at handover
At handover you should receive a complete compliance pack, not just a single certificate. On every new build we hand over:
- QBCC Form 4 plumbing compliance certificate
- Gas compliance certificate for every gas appliance installed
- Hydrostatic pressure test certificate
- Backflow prevention testing certificate, if backflow devices were installed
- Hot water unit warranty registration in your name
- As-built drainage drawings
- Workmanship guarantee documentation
It is handed over as a single PDF pack, lodged with the relevant authorities, ready for your certifier to issue the certificate of classification. File it with your house paperwork, because you will need it for the certificate of classification, future insurance claims, the sale of the house, and any future plumbing work where the existing system is being modified.
How inspection scheduling affects your build timeline
The inspections themselves are quick, but the scheduling of them drives a chunk of the build program that owner-builders often underestimate. A pre-slab drainage inspection typically needs several working days' lead time. Septic and AWTS inspections on acreage builds can need longer in the busy period. If you stack several inspections across the build and each adds waiting time, that becomes weeks of elapsed time inside the headline build timeline. We book our inspections as soon as we have a date for the work, often weeks ahead, and we keep an inspections diary so the build never waits on a missed booking. Owner-builders managing this themselves should set reminders well before each inspection trigger point.
What happens if an inspection fails
If an inspection finds a defect, the work has to be corrected and re-inspected before the build can progress past that point. On pre-slab that means fixing the drainage before the pour, which is the whole point of inspecting before the concrete goes on. A failed inspection caught at the right stage is cheap to fix. The same defect discovered after the slab is poured or the walls are sheeted is expensive. This is exactly why the staged inspection regime exists, to catch problems while they are still accessible. A good licensed plumber gets the work right the first time so inspections pass cleanly, which keeps the build moving.
Get the inspections planned into your build
The inspections are not something to leave to chance or to book at the last minute. They need lead time and they need to sit in the right place in the program. We plan the plumbing inspections into the build from quote stage, book them ahead, and hand you a complete compliance pack at handover. For the full build picture, read our new build plumbing guide and the stages guide, see our new build plumbing service, or get in touch and we will walk you through what your build needs.