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Septic Tanks

The Shire's Regulatory Services Department works to ensure onsite wastewater systems do not pose an environmental or public health threat.

Septic tank installations must be applied for and assessed by the Shire of Irwin’s Environmental Health Officer (EHO) before any works can commence.   This includes both combined effluent disposal systems at premises where sewer is not available, and also greywater re-use systems which may be installed in either sewered or unsewered areas.

Septic tank applications

The EHO needs to assess the application in accordance with the following;

  • systems to be installed must have approval for use in Western Australia by the Department of Health
  • construction of the apparatus shall be in accordance with the requirements of the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974
  • approval will not be given for the installation of an apparatus where a sewer connection is available as provided for by the Heath Act 1911.

 How do I lodge my application and pay fees?

Depending on the requirements of the application, either the Shire of Irwin will approve the application or it may need to be sent to the Department of Health for approval.

Applications are to be submitted using the Heath Departments Application to Construct or Install an Apparatus for the Treatment of Sewage form. Each application must be accompanied by payment of the application and inspection fee.

Each application must be accompanied by 2 sets of plans where Shire approval only is required and 3 sets of plans where approval from the Department of Health is required.

Drawings are to include the following;

  • Scale of drawing, either 1:100, 1:200 or 1:500
  • Location of effluent disposal system and all drains and pipework
  • Indicate the size of the tanks
  • Distance of the system from all buildings, boundaries, bores, waterway and waterbodies
  • Distance of system from all trafficable areas
  • Site plan to have contour lines indicating the slope of the land

Note: Any change from what has been approved must be reviewed by the Shire before installation, which may require the submission of amended plans.

Application to Construct or Install an Apparatus for the Treatment of Sewage

Approval to Construct or Install

Once your application is approved you will receive an APPROVAL TO CONSTRUCT OR INSTALL AN APPARATUS FOR THE TREATMENT OF SEWAGE.  You must not conduct works until you receive your approval.


Once the system is installed it MUST BE INSPECTED by the EHO before the system is covered, please contact the Regulatory Services Department for inspection details. 

A Compliance Certificate from the Plumber also needs to be provided to the Shire at this stage.

Permit to Use

Once your system has been inspected and has been installed correctly, you will then receive a PERMIT TO USE, your system is then considered authorised and ready to use.

Note: It is an offence to use a system without a permit to use.


When a developed property is connected to sewer, any onsite effluent disposal systems such as septic tank and leach drain/soakwell systems will eventually require decommissioning.

This requires that the contents of the tank are pumped out by an approved contractor and the system either removed or backfilled. If the system can't be removed, the tanks should be pumped out, the bottom of the tanks broken up and the system backfilled with sand.

As there are costs involved in both decommissioning a septic tank and connecting to sewer, householders are not automatically required to decommission tanks when they connect to the sewer. Under the Health (Treatment of Sewage and Disposal of Effluent and Liquid Waste) Regulations 1974 decommissioning is required when:

  • The property is sold
  • The use of the development changes e.g. from a residence to a child care centre
  • Building extensions may encroach on minimum setback requirements for the system

Septic tanks which have not been decommissioned must not be paved or built over without approval from the Shire.

The Shire requires notification to be forwarded when a system has been decommissioned. Please forward a letter to the Shire with a copy of the certification from the liquid waste contractor.

For further information on requirements around decommissioning septic tanks, visit the Department of Health website.

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