Septic Tanks

​​​​​​The majority of areas within the City of Kwinana are connected to the sewer network, however the rural areas often require on-site effluent disposal systems to be installed.​

Conventional septic systems generally comprise of two septic tanks and two leach drains or four soak wells. 

Nutrient-retentive effluent disposal systems can include aerobic treatment units (ATU) that incorporate an aeration system to break down waste to effluent and be further disposed into an irrigation field or leach drains. It can also include nutrient removing systems that use septic tanks with discharge of effluent through amended soils. 

There are a number of relevant legislations, policies and guidelines that govern the installation, operation and maintenance of effluent disposal systems:

Selecting an effluent disposal system

Conventional septic systems are no longer approved in the City of Kwinana. Only certain approved wastewater systems can be installed within the City of Kwinana environmentally sensitive areas including areas within the Peel Harvey Catchment or Cockburn Sound Catchment.

For a list of approved nutrient retentive effluent disposal systems (Aerobic Treatment Units or Alternative Leach Drains), please visit the Department of Health’s website.​

Unless sewer is available on the property, the following areas are required to be connected to nutrient retentive effluent disposal system to ensure that phosphorous or nitrogen does not impact on natural water bodies. 

  • Wellard (West of Freeway), Kwinana Beach, Naval Base, Hope Valley, Postans and Mandogalup – total nitrogen (TN)
  • Wellard (East of Freeway), Wandi, Casuarina, Anketell – total phosphorus (TP)

You can contact the Water Corporation to check if your property is connected to sewer or have availability to sewer by telephone on 13 13 95 or online. ​

Application to Install an Effluent Disposal System

All onsite effluent disposal systems installed within the City of Kwinana must be assessed and approved by the Manager Environmental Health Services.

The installer should complete the Application to Construct or Install an Apparatus for the Treatment of Sewage​​​ and submit with the prescribed fee, plans and specifications. This fee is made up of two charges, these being a fee for an 'Approval to Construct an Apparatus' and a fee for a 'Permit to Use' an apparatus once it is installed. 

Applications for multiple dwellings and premises that produce more than 540L of sewage per day must be approved by the Department of Health. Additional fees apply in these cases as a Local Government Report will need to be prepared. ​​

Please note that it is illegal to use an onsite effluent disposal system unless it has been approved for use by an Authorised Officer and a 'Permit to Use' has been issued.

Decommissioning of Septic Tanks

When a property is connected to mains sewer, the property owner is required to decommission the existing septic tank and effluent disposal system when the following circumstances arise:
  • there is a change of ownership of the property. Accordingly, the new owner has 60 days to decommission the septic tank apparatus;
  • here is a material change in the use of the premises. Accordingly, the owner has 60 days to decommission the septic tank apparatus; or
  • if the foundations for a building on the premises are to be built closer than 1.2m to the septic tank apparatus or a building is to be constructed above the septic tank apparatus or closer than 1.8m to any leach drain or soakwell. Accordingly, the owner shall decommission the septic tank apparatus before the building work commences
Decommissioning means that:

  • all septic tanks, soakwells and/or leach drains are pumped empty by a licensed Liquid Waste Contractor; and
  • all empty septic tanks, soakwells and/or leach drains must be either removed or have their lids and bases broken and filled with clean sand.

Please read the Decommissioning Guidelines​ for further information.​​
Page reviewed: 13 Jan 2020 8:51pm