GRAF Australia
Quote
Sponge-city stormwater concept showing on-site detention and infiltration for Australian developments

GRAF Australia

OSD & stormwater guide

OSD tank Australia: on-site detention for council peak-flow rules

An OSD tank holds stormwater on site and releases it at a controlled rate. Separate detention from reuse, compare EcoBloc and tanks, then quote GRAF Australia.

Request a project quoteCall 1300 131 971

In short

An OSD tank (on-site detention) temporarily stores stormwater and releases it slowly so developments meet council peak-flow limits. It is not a rainwater reuse tank. In Australia, GRAF EcoBloc modular crates and Carat/Platin detention tanks are engineered options for commercial and civil sites. Specify with your civil design, then buy and quote through GRAF Australia (grafaustralia.com.au, 1300 131 971).

How it works

Runoff enters underground detention volume, then leaves through a controlled outlet sized to the permitted discharge rate.
OSD tank and stormwater detention flow diagramCatchment runoff from roofs and hardstand flows into underground OSD or detention storage, then discharges through a controlled outlet sized to the permitted rate.Roof / hardstandCatchment runoffOSD / detentionEcoBloc or tank volumeHolds peak storm flowControlled outletCouncil peak-flow limitNot the same as a rainwater reuse tank

What to do next

  1. 01

    Confirm the planning condition

    Read whether the consent asks for OSD, detention, attenuation, retention or rainwater reuse. Wrong product selection usually starts here.

  2. 02

    Get a civil volume

    Your engineer sizes volume from catchment, rainfall and permitted discharge against the local OSD policy. GRAF design tools support a first pass.

  3. 03

    Choose EcoBloc, tank or hybrid

    Match footprint, cover depth, load class and inspectability. Request a GRAF Australia quote with plans and location.

What an OSD tank does

On-site detention holds runoff from roofs, paving and hardstand during a storm, then discharges at a controlled rate. Councils use OSD policies so new developments do not overload downstream pipes and waterways.

OSD is not rainwater harvesting. If your consent condition says detention, attenuation or OSD, you need a detention design. If it says reuse or rainwater tank, use the underground rainwater guide instead.

GRAF Australia stormwater detention products staged for national project dispatch
GRAF Australia supplies detention hardware nationally with state sales support.

Detention, retention and infiltration

Detention holds and releases at a controlled rate. Retention holds volume longer (sometimes for reuse). Infiltration returns water to soil where geotech and contamination rules allow. Australian briefs often mix these under WSUD or OSD labels.

Clarify the authority requirement before you lock a product family. GRAF Australia helps match EcoBloc crates, detention tanks or hybrid packages to the real brief.

GRAF EcoBloc and detention tanks

EcoBloc modules assemble into underground storage under car parks and hardstand with a flexible footprint. Inspect Smart variants support maintenance access, which councils and asset owners often require.

Carat and Platin stormwater detention tanks provide vessel-style volume when a tank geometry suits the design. Load class, cover depth and liner details must follow GRAF guidance and the certified civil design.

GRAF manufacturing of polyethylene detention tanks for Australian load and climate conditions
Engineered poly systems adapted for Australian load and climate conditions.

Compare options

High-level choice guide for Australian OSD and detention briefs.

OptionBest whenWatch-outs
EcoBloc cratesLarge footprint under pavement; need modular volume and inspectabilityNeeds certified cover, geotextile/liner and O&M access
Carat / Platin detention tankVessel geometry preferred; discrete tank volumeConfirm cover depth and traffic load class
Concrete OSD tankCivil spec demands monolithic concreteHeavier install; compare programme and access
Rainwater reuse tankConsent is harvesting, not peak-flow controlDo not substitute for OSD without engineer sign-off

Specify these products

Frequently asked questions

What is an OSD tank?+
An OSD tank (on-site detention tank) temporarily stores stormwater runoff on a development and releases it at a controlled rate so peak flows to the street or waterway stay within council limits. In Australia, OSD is a common planning condition for new residential and commercial projects.
What does OSD stand for?+
OSD means on-site detention (sometimes written on site detention). It is a stormwater control measure, not the same as a rainwater tank used for reuse.
OSD tank vs rainwater tank: what is the difference?+
An OSD tank detains runoff and discharges slowly to meet peak-flow rules. A rainwater tank stores water for reuse (irrigation, toilets, laundry). Some sites need both. Confirm the planning condition before you specify products.
What is a stormwater detention tank in Australia?+
A stormwater detention tank (or modular detention system) holds runoff from roofs, car parks or hardstand and releases it at a controlled rate. GRAF Australia supplies EcoBloc modular crates and Carat/Platin detention tanks for Australian OSD and WSUD projects.
EcoBloc vs concrete OSD tanks: which should I use?+
EcoBloc builds volume with lightweight modular crates under pavement or landscape, with inspectable options for maintenance. Concrete tanks are monolithic vessels. Choice depends on load class, depth, footprint, inspectability and programme. GRAF Australia can compare EcoBloc and Carat detention for your civil brief.
How do I size an OSD tank for a commercial site?+
Sizing follows catchment area, rainfall intensity, permitted site discharge and the local council OSD policy. Use GRAF Australia OSD and stormwater design tools for a preliminary volume, then engage your civil engineer for certified design and request a product quote.
Where can I buy OSD or stormwater detention tanks in Australia?+
Quote and buy through GRAF Australia at grafaustralia.com.au or call 1300 131 971. Trade partners including Reece may supply selected lines. Local AU support is GRAF Australia; graf.info holds global engineering references.
Do EcoBloc detention systems need maintenance?+
Yes. Sediment and debris management should follow the project O&M plan. EcoBloc Inspect Smart modules are designed so inspection and cleaning remain practical after handover.

Need an OSD or detention quote?

Send plans, required volume and location. Call 1300 131 971 or use the quote form.

Request a quote