Fabricated in Australia to German DVS standards · ISO 9001 certified by SGS · Trading since 1971
Commercial stormwater detention tanks, custom fabricated. On-site detention (OSD) tanks for commercial, industrial, basement and civil projects, in structured twin-wall HDPE and polypropylene, built to your approved hydraulic design: exact volume, exact footprint, orifice and overflow to specification. We fabricate where no catalogue tank fits the space. We do not supply tanks for houses or townhouses; a rotomoulded or precast unit is the right product there. Fabricated in Brisbane to German DVS standards, trading since 1971, ISO 9001 certified by SGS, delivered Australia wide.
What is a stormwater detention tank?
A stormwater detention tank is an engineered vessel that temporarily holds runoff during a storm and releases it to the public drainage network at a controlled rate. Urban development replaces absorbent ground with roofs, driveways and hardstand, so runoff arrives at the street drainage in one surge and raises flood risk downstream. Most Australian councils therefore require on-site detention as a condition of development approval for commercial, industrial and multi-storey developments and for civil works.
The hydraulic design is set by your consulting engineer to the council’s requirements: a required storage volume and a permissible site discharge (PSD), calculated using Australian Rainfall and Runoff (ARR 2019) methods and detailed to AS/NZS 3500.3. Industrial Plastics fabricates the tank to that approved design.
Detention is not retention. A detention tank empties completely between storms through an always-open outlet, so full capacity is available for the next event. A retention or rainwater tank stores water for reuse.
How a stormwater detention tank works
- Collection. Runoff from roofs, car parks and hardstand is piped into the tank during rainfall.
- Temporary storage. The tank absorbs the peak inflow that would otherwise overwhelm the street drainage.
- Controlled release. Water exits through a precision orifice plate sized to the permissible site discharge, typically a fraction of the peak inflow rate.
- Drain down and overflow. The tank drains empty between events, and an emergency overflow handles storms beyond the design capacity.
Why developers and engineers choose Industrial Plastics
1. Fabricated to German DVS standards, global best practice
Every panel, seam and pipe connection is fabricated to the relevant DVS standard:
- DVS 2207, HDPE and PP butt-fusion and extrusion welding, the international benchmark for joint integrity and leak-free service
- DVS 2205, construction of thermoplastic tanks and apparatus (load calculations, wall build-up and seam validation)
- DVS 2210, industrial thermoplastic pipework systems
What this means for you: a detention tank spends its life buried under a slab or car park, where a failed joint means excavation. DVS fabrication gives you a fully welded, monolithic vessel with no gaskets, no mechanical joints and no glued seams under the ground. See our DVS 2207 welding and DVS 2205 tank design standards.
2. ISO 9001 certified by SGS since 2008
Our quality management system is independently certified by SGS. Every tank leaves the workshop with material traceability, weld records and dimensional verification, the documentation your superintendent or certifier expects when signing off an OSD asset that will be buried and forgotten for decades.
3. Structured twin-wall sheet, engineered in Germany
We fabricate detention tanks from structured twin-wall sheet by Röchling (Polystone CubX) and SIMONA, Europe’s leading thermoplastic sheet manufacturers. Two smooth cover sheets are welded over an internal rib structure that works like an I-beam: manufacturer data shows a 57mm CubX sheet matches the stiffness of a 35mm solid PP sheet at roughly half the weight. That rigidity lets us build large rectangular tanks with minimal or no steel reinforcement, in wall build-ups from 41mm to 100mm matched to the burial depth. Panel selection and seam design are verified with the manufacturers’ calculation tools (Röchling RITA, SIMONA SIMOstatics) to DVS 2205.
4. Custom fabrication since 1971
Every detention tank is built to the drawing, not taken off a shelf. Any footprint, any depth, single or multi-chamber, right-angle and L-shaped plans to thread between piles and footings, and sectional fabrication where basement access rules out a one-piece tank. That flexibility is why builders come to us when a modular product will not fit the space.
What we fabricate
| Configuration | Typical application | Materials |
|---|---|---|
| Single-chamber detention tanks | Commercial sites with a single catchment and simple discharge | HDPE (PE100) structured twin-wall |
| Multi-chamber baffled tanks | Larger volumes, sediment control, staged discharge | HDPE, polypropylene |
| Basement detention tanks | High-rise and podium projects with no external space, built in sections and welded in place | Polypropylene, PPs (flame-retardant grade where specified) |
| Trafficable buried tanks | Installation beneath car parks and driveways, structural design coordinated with your civil engineer | HDPE structured twin-wall |
| Pretreatment chambers | Sediment traps and first-flush capture ahead of the main storage | HDPE, polypropylene |
| Outlet control | Precision orifice plates, weirs and multi-stage outlets sized to the PSD | PVC-u, HDPE |
| Access hardware | 600mm telescopic manhole chutes, trimmed to finished level on site | HDPE, polypropylene |
Material selection guide for detention tanks
Buried stormwater duty is a structural problem more than a chemical one. Quick reference:
| Material | When to specify | When NOT to |
|---|---|---|
| HDPE (PE100) structured twin-wall | Default for buried detention tanks. Impact tough, fully weldable, stable in ground water and repairable in service. | Continuous service above 60°C |
| Polypropylene (PP-H) twin-wall | Higher stiffness where the structural design calls for it, basement installations. | Cold-climate impact duty; UV exposure without stabilisation |
| PPs (flame retardant) | Basements and fire-sensitive buildings where the fire engineer requires a low-flammability material. | General buried duty (unnecessary cost) |
| PVC-u | Pipe spigots, orifice plates and outlet fittings. | The tank shell itself |
Not sure which? Send us the approved OSD design and we will spec it for you. Or use our Tank Capacity Calculator and Chemical Compatibility Checker.
Structured twin-wall vs modular crates and concrete
Most OSD systems on the market are modular crate assemblies or precast concrete units. A welded structured-sheet tank is a different class of asset:
| Feature | Welded structured-sheet tank | Modular crate system |
|---|---|---|
| Structure | Monolithic, fully welded vessel, seams designed to DVS 2205 | Interlocking units with many connection points |
| Sizing | Any footprint, depth and shape, fabricated to the drawing | Limited to module increments |
| Long-term load behaviour | Panel build-up engineered for sustained soil and traffic load, verified with manufacturer FEM tools | Documented failures under sustained load, with thermoplastic creep cited as an initiating factor |
| Inspection and maintenance | 600mm manhole access, internal inspection and silt removal | Limited or no internal access |
| Quality control | Workshop fabrication, weld testing, leak testing before dispatch | Assembled in the excavation, quality depends on site conditions |
Against precast concrete: a welded plastic tank is a fraction of the weight (lighter cranage and faster placement), immune to sulfate attack and carbonation, and can be delivered in sections through confined access and welded on site. Precast remains a fair choice for standard pit formats; custom footprints, basement retrofits and aggressive ground conditions are where welded thermoplastic wins.
Where our detention tanks are used
Basements and podium decks
High-rise and mixed-use projects where detention must sit inside the basement. We fabricate in transportable sections, carry them through standard access and weld the tank together in place, in flame-retardant PPs where the fire engineer requires it.
Commercial and industrial sites
Warehouses, showrooms, distribution centres and processing facilities with large roof and hardstand catchments. Multi-chamber tanks with pretreatment, sized for large storage volumes and trafficable installation beneath car parks.
Civil and infrastructure
Depots, transport facilities and public projects needing durable, inspectable detention assets with full QA documentation. See our civil and landscaping capability.
Retrofits and non-standard sites
Council conditions that arrive after the structure is built, failed crate systems that need replacing, and footprints threaded between piles, footings and in-ground services. Sectional fabrication and on-site welding are what make these jobs possible.
Engineering and design features
| Feature | Detail |
|---|---|
| Outlet orifice | Precision-cut orifice plate sized to the permissible site discharge, replaceable if the design changes |
| Internal baffles | Flow control, sediment settling and structural stiffening in long tanks |
| Emergency overflow | High-level overflow sized for events beyond the design storm |
| Access | 600mm telescopic manhole chutes, trimmed to finished surface level on site |
| Pretreatment | Sediment traps and first-flush chambers to keep silt out of the main storage |
| Buoyancy restraint | Buoyancy check at design stage; anchoring or ballast detail where the water table demands it |
| Traffic and soil loading | Panel build-up engineered for burial depth and surface loading, coordinated with your civil engineer |
| Sectional fabrication | Transport-friendly sections welded on site for basements and confined access |
Standards and compliance, at a glance
| Standard | What it covers |
|---|---|
| ISO 9001:2015 (SGS) | Quality management: material traceability, weld inspection, dimensional QA, finished goods |
| DVS 2207 | HDPE and PP welding (butt-fusion, extrusion), the international benchmark for joint integrity |
| DVS 2205 | Thermoplastic tank and apparatus construction: load, wall build-up, seam design |
| DVS 2210 | Industrial thermoplastic pipework systems |
| DVS 2212-1 | Welder qualification testing |
| ARR 2019 | Hydrologic design methods used by your consulting engineer to size the storage and discharge |
| AS/NZS 3500.3 | Stormwater drainage design and installation |
| Local council OSD requirements | Vary by council; we fabricate to your approved design and supply QA documentation |
Projects we quote, and projects we do not
We are a custom fabricator, not a tank retailer. The economic case for a welded structured-sheet tank is strongest where no off-the-shelf product fits.
We quote
- Basement and podium deck detention tanks, built in sections and welded in place
- Trafficable buried tanks beneath car parks, loading docks and driveways
- Multi-chamber tanks with pretreatment and staged discharge
- Replacements for failed or non-compliant crate systems
- Civil, transport and public infrastructure projects requiring full QA documentation
- Any footprint, depth or shape that no catalogue poly or precast tank matches
We do not quote
- Single dwelling, duplex and townhouse OSD
- Standard rectangular or slimline tanks available off the shelf in the required size
- Rainwater and retention tanks for reuse
What we need to quote
Send what you have. A complete set lets us price in one pass; a partial set gets a budget figure and a list of what is still needed.
- Approved OSD design or hydraulic report: storage volume, permissible site discharge, orifice size, overflow level
- Site plan: available footprint, invert levels, finished surface level, depth constraints
- Loading: burial depth and whether the surface is trafficable, and to what vehicle class
- Ground conditions: water table and geotechnical report if available
- Access route for basement or confined installs: door, lift and corridor dimensions, so we can size the sections
- Fire engineering requirement for basement tanks, if PPs flame-retardant material is specified
- Delivery location and program dates, and any drawings as PDF, DWG or ZIP
Frequently asked questions
Your council sets the requirements and your hydraulic consultant calculates the storage volume and permissible site discharge using ARR 2019 methods. We fabricate for commercial, basement and civil projects where the required volume or footprint is beyond what a catalogue tank can supply. We build to the approved design, and our Tank Capacity Calculator is a quick way to convert a required volume into a footprint that fits your site.
No. Single dwelling, duplex and townhouse OSD is well served by rotomoulded poly and precast concrete tanks sold off the shelf, and those are the economic choice at that scale. We fabricate where no catalogue tank fits: inside basements and under podium decks, beneath trafficable car parks, in irregular footprints between piles and services, and on civil and infrastructure projects that need full QA documentation.
A detention tank holds stormwater briefly and releases it at a controlled rate through an always-open outlet, draining empty between storms. A retention tank stores water for later reuse. Councils mandate detention to protect the drainage network; retention is about water supply.
Yes. Structured twin-wall tanks are installed beneath car parks and driveways. The panel build-up is engineered for the burial depth and traffic loading to DVS 2205, and the installation detail (bedding, backfill, cover slab where required) is coordinated with your civil engineer.
Yes. We fabricate the tank in sections sized to your access route, then weld it together in place. This is a common solution for high-rise and podium projects, and for retrofits where council conditions arrive after the structure is built.
A welded structured-sheet tank is a single, monolithic vessel with engineered wall panels, tested seams and manhole access for inspection and silt removal. Crate systems assemble hundreds of interlocking units in the excavation, offer little internal access, and industry investigations have documented collapses under sustained load with thermoplastic creep cited as an initiating factor.
Sometimes. An empty tank in a high water table wants to float, so we run a buoyancy check at design stage and detail anchoring or ballast where required. Tell us your ground water conditions when you request a quote.
Typically three to six weeks from approved drawings, depending on size, complexity and site conditions. Confirmed at quote, with staged delivery available for multi-tank projects.
Yes. We fabricate at our Brisbane workshop in Hemmant and deliver nationally, with sectional fabrication for tight access and on-site welding support for large or basement installations. © 2026 Industrial Plastics Pty Ltd. Page version 1.1, November 2026.
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Get an engineered quote
Send drawings, a sketch, or a description of the duty. An engineer reviews every enquiry and confirms receipt within one business day.
Materials we work in for this
Commercial detention tanks use HDPE (PE100) structured twin-wall for buried duty, polypropylene for basement and flame-retardant applications, and PVC-u for pipe connections and orifice plates.
Choosing between tank types? Read rotomoulded vs fabricated plastic tanks and fabricated vs GRP / FRP tanks to see why engineer-specified, fully welded thermoplastic suits buried detention duty.