Approval of an On-Site Stormwater Detention System - New South Wales

Service summary

You may be required to apply for approval to install an on-site stormwater detention (OSD) system if you intend connect to or develop a property that connects to a Sydney Water stormwater asset or natural water. Properties that must have an OSD system include (but are not limited to):

  • all commercial, industrial and special use (e.g. community, education, recreational) buildings or structures
  • town houses, villas, home units or other strata subdivisions (these may use a single OSD system for the total site area as long as it?s located on common property and the body corporate is responsible for maintenance)
  • dual occupancy lots (each lot within the dual occupancy must have its own OSD system. Each individual lot owner is responsible for maintenance)
  • sealed sporting facilities (e.g. tennis, basketball courts).

The requirements imposed by Sydney Water are supplementary to any council guidelines. Please consult the Council and Sydney Water for more information.

Service type


A licence defines the need to obtain recognition / certification and registration to undertake a certain business activity.


You may be exempt from requiring an OSD system if:

  • you are building a single residential dwelling
  • the original total site area is under 250m2
  • the development site is at the lower section of the catchment
  • you are refurbishing an existing build and maintain the existing drainage system.

Eligibility requirements

Before you can begin construction you must submit:

  • certification of design by a chartered civil engineer, verifying that it has been designed to meet the calculated specifications
  • a plan and elevation of OSD system with all dimensions
  • the location of OSD storage in relation to overall development and site drainage
  • a detailed design of orifice including all dimensions, maximum storage discharge rate specifications and the percentage (if any) of the site area that will drain to the street or other stormwater system.

After construction of the OSD system is complete you must submit:

  • Work-As-Executed (WAE) plans prepared and signed by a registered surveyor
  • Certificates of Hydraulic Compliance that confirm the system has been constructed and will function as designed and identify any variations from the approved design, and state that these variations will not affect the performance of the OSD system.

Ongoing requirements

You must regularly maintain your OSD system to prevent potential problems.

If your OSD system discharges directly into a Sydney Water owned drainage system, you must enter into a formal agreement with Sydney Water which sets out your ongoing OSD maintenance responsibilities. You will need to register this agreement on the property title so the information is stored on the title of the land and not lost over time as properties change ownership.

If your OSD system discharges directly into a drainage system that is not owned by Sydney Water, you may be required to enter into an agreement with your local council.

Please contact your local council or Sydney Water for more information.



Please consult the Contact Officer for information on fees to be submitted.

Other resources

Administering agency

Sydney Water Corporation

Act(s) name

Sydney Water Act 1994 (New South Wales)

Regulation(s) name

Sydney Water Regulation 2011 (New South Wales)

Contact details

Online service for applications, approvals and diagrams.
Sydney Water Corporation

Contact us other:

1300 082 746

Sydney Water Corporation


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