In Part 2 of our plumbing series, we looked at the most common plumbing mistakes owner builders make once construction is underway and how to avoid them.
Now in Part 3, it’s time to talk rules, permits, and compliance. Yep, the paperwork part.
But before you zone out, hear us out. Understanding plumbing regulations isn’t just about ticking boxes. It’s about protecting your build, passing inspections, and avoiding costly rework.
Licensed plumber Nathan, from KNR Plumbing on the Sunshine Coast is back to break it all down in plain English.
One National Plumbing Code, Australia-Wide
Plumbing work across Australia follows the AS/NZS 3500 Plumbing Code, which applies no matter which state you live in.
“That’s the national standard we all work to. Every plumber in the country is meant to follow it,” Nathan explains. “Some councils and states may have additional guidelines, but the national code overrides them”.
🔧 Pro tip: Ask your plumber if they work to AS 3500, and check with your council for any extra local requirements.
Permits, Notifiable Work and Plumbing Inspections
There are two categories of plumbing work you need to understand:
- Notifiable Work – typically renovations. Doesn’t require formal council inspection but must be logged by the plumber.
- Permit Work – required for new builds, granny flats, or anything needing new sewer connections. This work must be inspected and signed off.
“For permit work, I organise all inspections. There’s one for drainage, one after rough-in, and one at the final fit-off,” Nathan says.
🔧 Pro tip: Ask your plumber to explain what type of work you’re doing and whether inspections are required.
Bum Guns and Backflow Prevention
Bidet-style spray guns (commonly known as “bum guns”) are rising in popularity but they come with strict rules.
“They’re classed as high hazard. To install one legally, you need an RPZ valve (Reduce Pressure Zone), which is big, ugly, and requires yearly servicing,” Nathan says.
These valves must also be registered with your local council, and many plumbers won’t install bum guns due to the risk and regulation complexity.
🔧 Pro tip: If a trade offers to install one without an RPZ valve, walk away!
Overflow Relief Gullies (ORGs)
Every house has an Overflow Relief Gully (ORG), a small grated drain outside your bathroom or kitchen. It’s a critical safety feature that prevents sewage from backing up into your house.
“People cover them with pot plants or try to lower them for aesthetics, but they must be above ground. Councils will flag them if they’re non-compliant.”
If your ORG is in concrete or paved areas, any fixes due to a plumbing problem could involve cutting and reworking surfaces.
🔧 Pro tip: Never cover or remove your ORG. It must be visible and raised (e.g. 75mm above ground in Sunshine Coast Council).
Wrapping It Up
Plumbing rules might not be the most exciting part of your build but they’re one of the most important. From backflow devices to ORGs, getting it right the first time means fewer headaches later (and fewer surprises at inspection).
In the next and final part of our series, we’ll explore how to confidently hire and work with a plumber, including tips on quoting, comparing estimates, and what to ask before you sign off.
About Nathan Rich – KNR Mechanical Plumbing
Nathan runs KNR Mechanical Plumbing on the Sunshine Coast and has built a solid reputation for being friendly, down-to-earth, and great at what he does.
With loads of experience in residential builds and renos, Nathan takes pride in doing the job right. No shortcuts, just honest advice and quality work.
If you’re after a plumber who actually cares about your build and has experience working with owner builders, Nathan’s your guy!
Need help with council regulations? Our Facebook group has over 12,000 Australian owner builders who’ve tackled it before. Click here to join the conversation today!
