City of Cockburn, PO Box 1215, Bibra Lake DC, Western Australia, 6965
Telephone: (08) 9411 3444

Effluent Disposal

We assess applications for on-site effluent disposal systems within the City.

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. 

The City of Cockburn will only consider applications for installation of an  on-site effluent disposal system where that system has been approved for use in Western Australia by the Department of Health. 

The type of system required at a property depends on a number of factors. The On-site Effluent Disposal Systems brochure has further information on such systems in the City.



Conventional Septic System

Conventional effluent disposal systems incorporate two septic tanks and two leach drains or four soak wells.

Septic tanks digest the solid and liquid waste into an effluent, which is discharged into the ground via the leach drains or soak wells.  

Please check the Department of Health WA for a list of approved wastewater systems

Suppliers of concrete septic tanks can be found in Yellow Pages .

More information can be found by reading the Understanding Septic Tank Systems brochure.

There are a number of requirements associated with the installation of an effluent disposal system, including setbacks and environmental factors. The Standard Systems brochure has further information.


Maintenance of Systems



Pump out the tanks regularly:

  • average 4 person household approximately every 4 years.
  • 2 person household approximately 8-9 years.

Alternate your leach drains each year. All domestic systems approved from 1990 and onwards have two leach drains and an alternating device to allow systems to rest.

Dispose of materials that do not break down readily (e.g. plastic bags, kitchen sponges, sanitary napkins, tampons, disposable nappies).

Dispose of old medicines, large amounts of disinfectant or other strong chemicals down the pipes leading to the septic tank. (Bleaches and detergents are acceptable if used in moderation).


Please be advised that only licensed liquid waste contractors can pump out septic tanks.

A list of contractors can be obtained from the Yellow Pages under Septic Tank Cleaning Services.  




Nutrient Retentive Systems

Nutrient retentive onsite effluent disposal systems are an alternative to conventional septic systems.  They can be installed in areas which are environmentally sensitive, or where untreated effluent would pose a public health risk, due to their ability to produce "cleaner" effluent.

Nutrient retentive systems are required in a number of areas within the resource zone due to high ground water levels and their close proximity to the Peel-Harvey Catchment Area.

Nutrient retentive onsite effluent disposal system are categorised into one of two types:

  1. Aerobic Treatment Units (ATU) incorporate aeration systems to aid in the breakdown of the waste to an effluent. The effluent is then further treated and disposed of either by surface irrigation, sub-soil dripper or leach drain system. Surface irrigation is not a preferred method of disposal within the City.
  2. Nutrient Removing Effluent Disposal Systems utilise septic tanks to process the solid and liquid wastes, however the effluent is discharged through an amended soil, which strips the effluent of nutrients. 

Please check the list of approved aerobic treatment units and nutrient removing systems for apparatus that are approved by the Department of Health WA for use. 

It is recommended that you contact the manufacturers of ATU's and nutrient retentive leaching systems to obtain further details on approved systems.




Greywater re-use systems

Greywater systems allow house holders to conserve water by re-using wastewater from bathrooms and laundries (greywater) on gardens and lawns on their property.

The Department of Health approves the design of greywater systems under the current legislation. These systems provide some treatment or filtration of greywater before disposal of the effluent through a sub-surface reticulation system.

A list of Approved Greywater Systems is available for your information. All greywater system installations must be approved by the City's Health Services.  Please complete the Application to Construct or Install an Apparatus For the Treatment of Sewage.  The City of Cockburn does not charge a fee for this approval.

Further information on greywater systems can be obtained here, or from the Wastewater Management Section of the Department of Health on          9388 4932.

The Water Corporation promotes the use of approved greywater systems for water conservation under the Waterwise Rebate Program. Rebates are only available subject to the terms and conditions of the program.  Visit the Department of Water website for further information on the rebates available.




Installation of Effuent Disposal Systems

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

Please complete the Application to Construct or Install an Apparatus For the Treatment of Sewage Applications must be submitted with the prescribed fee. 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 540 litres of sewage per day must be approved by the Department of Health. Additional fees apply in these cases. 

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

Copies of the layout of onsite effluent disposal systems within the City can be obtained from Council Administration.  Plans will only be released to the property owner, or the owner's agent.




Water Corporations Infill Sewage Program

A number of residential areas within the City of Cockburn are in the process of being connected to mains sewage. The Water Corporation drives the infill sewage program with Western Australia.

Further information on this program can be obtained from the Water Corporation website.




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).
  • There is a material change in the use of the premises (accordingly the owner has 60 days to decommission the septic tank apparatus).
  • 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.
  • 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.