SA Stormwater Regulations for New Builds (2026): Detention, Tanks & Compliance
Building a New Home in Adelaide?
Building a new home in South Australia now comes with stricter stormwater management requirements, and they've only tightened since the Planning & Design Code's water-sensitive urban design (WSUD) amendments were adopted in 2025, in two stages on 26 April and 25 September. If you're planning a new build, understanding these rules could save you thousands of dollars and prevent costly delays.
For the bigger picture on how it all fits together, start with our complete guide to stormwater management in Adelaide.
Treating Your Block as a "Mini-Basin"
Gone are the days when you could simply connect your downpipes to the kerb and call it done. Across SA, new homes are increasingly expected to manage stormwater on-site: what we like to call treating your block as a small "mini-basin", a water management system in its own right. The formal mechanism behind this is Ministerial Building Standard MBS 009 (On-site Retention of Stormwater), which lets the relevant authority require built-in retention for new dwellings. In practice that means incorporating:
- Retention systems to capture and store rainwater
- Detention tanks to slow down water release during storms
- Rain gardens to naturally filter stormwater
- Permeable surfaces like grid pavers instead of solid concrete
Designing this properly from day one is exactly the kind of work our stormwater systems team handles for new builds.
The Rainwater Tank Requirement
South Australia has required a plumbed rainwater tank on new homes (and extensions over 50 m²) since 2006. The tank must be connected to a genuine use (typically a toilet, water heater or laundry cold tap) and installed by a licensed plumber to AS/NZS 3500. On top of that, the Planning & Design Code generally seeks a tank of around 3,000 litres (or an equivalent on-site detention/retention system) for new dwellings.
A well-sized rainwater harvesting setup, often a "combo" tank that serves both reuse and detention, is one of the simplest ways to tick this box while lowering your water bills.
Technical Requirements Getting Stricter
Depending on your council and site, you may also need:
- Higher floor levels in flood-prone areas
- Hydraulic sign-offs from qualified engineers
- Correctly sized pipes (commonly DN100) chosen per AS/NZS 3500.3:2025 based on roof area and rainfall intensity, not just the minimum
- Designated overflow paths to direct excess water safely to the street
- Regular maintenance of tanks and orifice systems
Note that AS/NZS 3500.3:2025 is now the current edition of the plumbing and drainage standard for stormwater, replacing the 2021 version from 20 October 2025, so any new drainage design should be worked to it.
What This Means for Your Build
Volume builders often provide a "stormwater allowance" that can escalate quickly, and their default drainage solutions are typically the cheapest option: basic PVC pipes to the kerb. That might not meet current requirements, leaving you with unexpected upgrade costs. If you're working with a project builder, our new-build drainage service can review the plan before you're locked in.
The modern approach follows the principle of "catch it, slow it, store it, prove it", meaning you need to demonstrate your system works effectively before getting final approvals.
Smart Planning Strategies
To navigate these requirements successfully:
- Involve a stormwater specialist early in your design process
- Use combo tanks that serve both rainwater reuse and detention purposes
- Size pipes by calculation, not by habit: design to AS/NZS 3500.3:2025 to future-proof your investment
- Implement WSUD landscaping from the start rather than retrofitting
- Keep detailed documentation of all approvals and specifications
Summary
SA's current stormwater requirements represent a fundamental shift towards treating every new home as part of the broader water management system. While this adds complexity and cost to your build, proper planning and professional guidance can ensure compliance without budget blowouts.
Ready to tackle your new build's stormwater requirements? At Stormwater Plus, we specialise in designing compliant, cost-effective drainage solutions for Adelaide homeowners. Our expert team understands the latest SA regulations and can help you navigate the complexities of modern stormwater management. Contact us today for a consultation and ensure your new build meets all requirements without breaking the budget.