Choosing an effluent system and location

A number of factors can determine the type of system and location where a system can be installed on the lot.  Factors can include:

  • Soil types – noting possible clay or rock layers and groundwater tables
  • Distance to water courses and bores
  • Method of storm water management
  • Available space, including the slope of the land and how the development is laid out.

If you are building a new house then this is the time to also consider additional development such as pools, patios, sheds, rainwater tanks and driveways.

Find out about approved effluent disposal systems.

Onsite effluent disposal system application and approval

The Shire of Mundaring can approve most applications for on-site effluent disposal systems on single residential or small commercial premises (producing no more than 540 litres of waste water per day).

Two application forms are available for use, depending on whether or not the application will be processed by the Shire of Mundaring or the Department of Health.

Single house, single lot or commercial properties generating less than 540L/day

Complete and submit the following form to the Shire:

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

Commercial properties, second system or systems generating more than 540L

Complete and submit the following form to the Shire:

Department of Health's Application to Construct or Install an Apparatus for the Treatment of Sewage (PDF).

Please note:

  • Both the Shire and Department of Health fees need to be paid. View current the Shire's current fees and charges.
  • All applications are submitted to the Shire of Mundaring in the first instance. For those applications that require Department of Health approval, the Shire will make an initial assessment and forward to the Department of Health for final assessment.
  • If you require assistance in understanding the application form or process please contact us.

Maintaining an effluent disposal system

Property owners must:

  • Pump out the tanks on a regular basis*
    • Every four years for an average four person household; or
    • Every eight to nine years for a two person household
  • Alternate leach drains each year
    • All conventional systems approved from 1990 and onwards (or older systems that have been upgraded) have two leach drains and an alternating device to enable a leach drain to “rest” whilst the other is in use
    • As a rule of thumb the diverter needs to be switched over every 12 months
  • Service aerobic treatment units regularly
    • By an authorised service person
    • The service person submits the servicing report to the Shire upon completion
  • Not plant trees or plants that are known to have an invasive root system
    • Figs, ficus and willows are well known for doing great damage to septic systems
    • Check with your nursey if a plant is known to have invasive roots.

*Only licensed liquid waste contractors can pump out effluent disposal systems. Contractors are listed in the Yellow Pages under Septic Tank Cleaning Services.

Property owners or occupiers must not:

  • Dispose of materials that do not break down readily
    • For example: plastic bags, kitchen sponges, sanitary napkins or tampons, disposable nappies, ear buds, “flushable wipes” or large amounts of fats or oils
  • Dispose of old medicines, large amounts of disinfectant or other strong chemicals down the pipes leading to the septic tank
    • To do so may seriously affect or kill off the beneficial bacteria that is digesting the effluent
    • Bleaches and detergents are acceptable if used in moderation.

More information and contact

For more information or advice please contact the Shire’s Health Services on 9290 6742 or email