Guidance on applying for approval of installation of a commercial onsite wastewater system

This information is designed to assist you to complete an application to construct or install an apparatus for the treatment of sewage in accordance with the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974.

When is an application required?

On-site disposal of wastewater is required in areas where reticulated sewerage is not available.

An application must be lodged every time you intend to construct and install an apparatus for on-site wastewater disposal.

All applications must be lodged to the local government authority (LGA) in the first instance.

The LGA will process your application if the proposed apparatus will treat less than 540 L/day of wastewater OR the building to be serviced is a single dwelling.

If the wastewater volume received by the system is more than 540L/day and the building being serviced is not a single dwelling the LGA will assess your application and prepare a local government report.

The report and application will then be forwarded to the Department of Health (the Department) for processing.

Can I construct or install a wastewater system before I get an approval?

No. It is an offence to commence construction or installation of any wastewater system without an approval from either the LGA or the Department.

Can I use a wastewater system before it is approved?

No. Before you can use any wastewater apparatus, the LGA must inspect the system to ensure it is installed correctly.

If the installation is satisfactory, the LGA will issue a permit to use.

It is an offence to use the system prior to receiving the permit to use.

Will an approval to construct and install or a permit to use be given if I have used the wastewater system?

No. There is no provision in the legislation to provide a retrospective approval. It is possible that you may be directed to stop using and remove the apparatus.

Overview of information required

General requirements

The following should be provided with all applications:

  • completed and signed application form submitted  via email to
  • application fees:
    • LGA – a fee is payable to the local government for the district in which the apparatus will be installed
    • Department of Health – an additional fee is payable to the Environmental Health Directorate by credit card (payment methods are included in the payment options section of the application form)
  •  technical information as required by the application form.

Note: please contact your local government or the Environmental Health Directorate for information on fees.

Technical information

The information listed below is required to accompany an application for the installation of a commercial on-site wastewater system.

Nature of the project

The proposed project information is required:

  • type of the development
  • description of staged development, if planned
  • size of served facility
  • intended use of the building and the intended use of rooms within the building
  • proposed installation and methods of disposal/reuse of the final effluent.

Site and Soil Evaluation

It is strongly recommended that assistance of professionals be engaged to undertake a Site and Soil Evaluation (SSE) (that is, persons with tertiary qualifications in soil sciences, hydrology, engineering or similar).

The SSE should be carried out in accordance with AS/NZS 1547: 2012 On-site domestic wastewater management and the Guidance on Site-and-soil evaluation for Onsite Sewage Management.

Plans and specifications

A detailed plan of the on-site wastewater system, site plan and a building plan must be submitted.

All plans are to be drawn to a scale of not less than 1:200.

Below is an image of a site plan.

System plan

System drawings submitted for consideration must:

  • show dimensions
  • be accompanied by a list of all components
  • show the intended layout of the system including the typical sittings of:
    • tanks
    • chambers and control panels
    • pipes
    • inlet and outlet arrangements,
    • effluent application areas or discharge points
  • show the capacities of all system components
  • any other relevant details.

Site plan and building plan

A site plan must clearly show:

  • location of all:
    • buildings or proposed buildings
    • water tanks
    • swimming pools
    • driveways
    • excavations
    • stormwater drains
    • water pipes
    • easement drains
    • streams
    • water courses
  • details of any site modifications for example:
    • benching
    • cutting
    • filling
  • site boundaries and size of the lot including dimensions in metres or millimetres
  • key topographical features for example:
    • creek line
    • drainage line
    • slope of the land
    • direction of flow of stormwater
    • flood plains
  • distances from boundaries, watercourses, buildings to the existing and proposed on-site wastewater treatment and disposal systems
  • exact location of all fixtures and fittings.

Design details of the system

Design details of the wastewater system to be used, including details of the:

  • type of system
  • trade name, if any
  • manufacturer's name
  • design capacity of the system.

Note: The proposed treatment and disposal systems must be approved by the Department. Check the status of manufacturers and various products online or phone the Environmental Health Directorateon 9222 2000.

Description of treatment process

A detailed description of the selected treatment process and major components of system equipment must be submitted and accompanied by:

  • schematic flow diagram to indicate stages in treatment process
  • details of pre-treatment system when required, for example an oil separator or grease trap
  • disinfection method, if required.

Flow and load of effluent

Details must be provided of the sewage generating development including:

  • maximum number of persons using the system/occupancy rate
  • type of facility to be served and per capita daily wastewater flow rate
  • total hydraulic load
  • calculation of daily wastewater volume
  • composition of wastewater for example
    • blackwater
    • greywater
    • non-domestic characteristics.

Effluent quality

Quality of effluent, both before and after treatment, shall be demonstrated prior to land application or discharge in terms of the following characteristics:

  • biochemical oxygen demand (BOD)
  • suspended solids
  • free residual chlorine
  • faecal coliforms
  • pH
  • grease or oil.

Land application or reuse system

Treated wastewater can be reused or simply disposed of depending on the type of land application system that is used and the quality of effluent.

The disposal of the wastewater can be through:

  • a soil absorption system for example:
    • leach drains
    • soakwells
  • an irrigation system which is located on a dedicated disposal area (not for beneficial use)
    • subsurface
    • surface irrigation.

Wastewater can also be reused with appropriate treatment to the required standards and some management controls for a wide range of beneficial uses including:

  • industrial uses for example
    • cooling
    • dust suppression
  • non-industrial uses for example
    • irrigation of public open spaces and agriculture
    • toilet flushing.

All recycled water schemes must be approved by the Department of Health prior to implementation.

A separate application is submitted for the reuse of wastewater.

When the wastewater reuse, disposal or combination of both is proposed the following details of the land application area must be submitted:

  • type of land application system for example:
    • surface
    • subsurface
    • evaporation pond
    • leach drains
  • reason for selection and suitability of type of land application
  • sizing of land application area
  • layout of land application area.

Signed maintenance agreement

A signed maintenance agreement between the owner and the service provider must be submitted for:

  • ongoing servicing
  • pump out
  • emergency repairs.

Regular maintenance of any systems must be detailed in the maintenance agreement including frequency of maintenance and methods.

The property owner will be held responsible for the ongoing operation of the system and should make any tenant aware of their responsibilities.

This requirement does not apply to conventional septic tank systems.

Certified engineering specification

Certified engineering specification of commercial wastewater treatment plants and treatment ponds must accompany applications where these are proposed.

Incomplete applications

The Department of Health and LGA can only assess complete applications.

If your application does not include all the necessary information and supporting plans it will be returned to you.

More information

  • Environmental Health Directorate
    Postal address: Department of Health, PO Box 8172, Perth Business Centre WA 6849
    Telephone: 9222 2000
Last reviewed: 26-11-2020
Produced by

Environmental Health Directorate